I suspect what I'm going to say may not be quite what you want to hear, but before you get upset with me over anything below, let me tell you something of my background.
I was baptized at 8, and the same day I was baptized a convert, a man in his early 20's, was also baptized in the same service. He was a faithful member and we became friends. He was like an older brother to me. He lived with my family for a short time, sharing my bedroom with me. One day my parents sat me down and told me he died, hit by a truck while crossing the street. His was the first funeral I ever went to. Later, when I was 16 I found out the truth. He was sexually attracted to other men. He stayed with us because the Branch President asked us to take him in to get him away from his non-member parents who rejected him, and he deliberately jumped in front of that truck.
Please understand that I am not unsympathetic to the challenges faced by those who on one hand have a real testimony of the church, and on the other hand have a sex drive that pushes them towards sin. But that situation is not limited to LGBTQ members. Sexual self control is a requirement for everybody, gay or straight. Some straight members find themselves unable to find a mate, other find themselves in a marriage where due to health reasons their spouse is not sexualy available, some are married to a spouse who has false ideas of sexuality, or past sexual traumas that lead them to constantly refuse sexual contact. Some people suffer from sexual addiction and everything that one spouse can offer is never going to be enough to satisfy them. None of those members are justified by their circumstances in breaking the law of chastity.
Some people find themselves having to choose between giving up sexual fulfillment for the sake of living the gospel, or giving up living the gospel for the sake of sexual fulfillment. Christ said:
Wherefore if thy hand or thy foot offend thee, cut them off, and cast them from thee: it is better for thee to enter into life halt or maimed, rather than having two hands or two feet to be cast into everlasting fire. And if thine eye offend thee, pluck it out, and cast it from thee: it is better for thee to enter into life with one eye, rather than having two eyes to be cast into hell fire. (Matt 18:8-9)If it is better to lose your hand, foot or eye to ensure salvation I think it is safe to assume it is better to do without sinful relationships and enter into heaven, than to indulge in them and burn. Our mortal bodies are temporary, the problems they bring and the temptations that pull at them are temporary situations. Damnation is eternal.
As for the three choices, there are cases of faithful gay members who have achieved mutually happiness in a heterosexual marriage. Rare, yes, but not impossible. I would not recommend across the board, but I wouldn't recommend automatically writing off the possibility either. Perhaps a marriage of a gay and a lesbian Mormon would fare better. They may not have erotic love but they can have companionship. They may not have passion but they can have sexual release, and children as well. They would each understand the struggle the other faces. But in my opinion any heterosexual marriage involving one or more gay people should only be considered when both know the situation up front and both have a strong confirmation from God that he approves.
Celibacy is challenging, but God would not give a person a challenge that is greater than they can bear. Everybody has to do without something, everybody has a cross to bear and for all we know, we each agreed to the challenges we would have before we came here. Not all challenges are equal, but we are promised God will make us equal to our own challenges if we let Him. The Apostle Paul was widowed and remained celibate the remainder of his life as he buried himself in spreading the gospel. Celibacy can be seen as an opportunity to devote your life to something good without the obligations of raising and providing for a family. In other faiths, there are those who willingly choose such a life.
If however a person chooses a romantic partner of the same sex, knowing what the church teaches, then yes, that is apostacy, it is rebellion against God. I agree that such a person can believe in other parts of the gospel, but they are still doing something fundamentally opposed to the gospel plan as well as putting their sexual desires above obedience to God. There is a huge inconsistency in their mind to try and maintain faith in something that says what they are doing is horribly wrong and at some point that will have to be addressed, either by rejecting the gospel further or conforming to it. A double minded man is unstable in all his ways (James 1:8)
The new policy changes absolutly nothing for faithful LGBTQ members who are living the commandments. For others it clarfies how far they have strayed from the path. They were in violation of the law of chastity beforehand. Serious sexual sins, gay or straight, will result in excommunication or other church discipline. Labeling it as apostacy isn't a matter of changing what it is, it a matter of making it clear to everybody what it is, what it has always been.
The Church has done much to express love for LGBTQ members, but pandering at the expense of the truth is not love. One truth is that same sex marriage is a grievous moral wrong, and while we embrace with love the sinner, we reject with clarity the sin. If somebody chooses to link accepting their sin with having love for them, they create a situation where they cut themselves off from feeling the love that the Church and God extent to them.
The children being raised in same-sex marriages are free to attend Primary, Youth Acitivites, Seminary etc. They can recieve priesthood blessings of comfort and blessings for the sick. If they want to serve a mission, there is a way for them to do that. Nothing that they are restricted from will put their exaltation at risk in the end.
Wickedness was never happiness, and those LGBTQ members who are unhappy over this are feeling the natural results of their sins. If they want to place blame, it belongs on the choices they themselves made. By forming such a household and bringing children into it they have negatively affected the lives of their children, and in more ways that what this policy does. That pain should motivate them to look at their life and bring into conformity with the gospel. While that will require sacrifice (as it does for all) it also brings happiness. If they persist in their apostacy, they will bring more unhappiness on themselves. Others who feel hurt over it are not understanding why this is right and necessary and loving.
Please understand I am not trying to discount anybody's pain, or sneer at them in a 'getting what they deserve' kind of way. I want everybody to share in the joy of the gospel and I sympathize with the emotional impact this has on people, but emotion doesn't change right and wrong, moral and immoral. The joy of the gospel comes by living it, even when it requires great sacrifice.
There is no love or joy in trying to make the sinner feel comfortable in their sins. No sad story from any member over how hurt their feelings are changes that. I'll happily put my arm around the shoulder of somebody hurting from this and tell them I know it's hard to bear, but if they do the right thing, hard as it is, they will be glad they did and I'll do what I can to help that happen. I will not say anything that would make them feel justified in continuing to do what they should not do.
So, if you really do have faith that this is the true church, lead by a prophet of God by revelation, than let go of your hurt and feelings of offense, humbly put your unrighteous desires aside and accept the new policy as being correct. Change your life to conform to gospel standards in whatever manner seems best for you. Doing any other thing will not bring you the happiness you want. I know it's easy for me to say this and incredibly hard for you to do it but it is still true. God will help you do it and so will many other members of the church if they can.