I don’t think you’re a monster. I do think your plate is way too full. Let me see if I can help you set some priorities.
Your son is 27. You didn’t tell me why he can’t work. Apparently Social Security doesn’t think he qualifies for benefits and should get a job. Unless he is incapacitated, it seems reasonable to me that he should either be working or he should be getting some schooling so that he can.
I’m confused: I can’t tell whether it is your husband or your father-in-law who is ill. I do understand that you have become a primary caregiver and the primary financial contributor in the family. That’s a very big load. If your son can’t work or go to school for some reason, the very least he could do is take on a big share of the care-taking. Regardless of gender, he can earn his keep by lightening your load.
At 27, your son’s decisions about his sexual identity are his own. All you have to do is love him as your child. You needn’t get involved in the apparent inconsistencies that are part of his struggle or in his decisions. You needn’t get between him and his father either. They need to work out their relationship themselves in order to own it.
Love your child. Love your husband. Express your confidence to both of them that they have what it takes to figure it out. Then have faith in them and take care of yourself by staying out of it.
Easier said than done, I know. But I also know that you can’t do all you are doing and be their counselor too. If they need help, encourage them to see a professional family therapist to help them sort things out. You are simply too over-stressed — and you are too close to the situation to be helpful.
I wish you well.