It's hard to say what affect it would have on infedility (because different couples have different standards as to what constitutes being unfaithful). However, I believe the divorce rate would be lower. I know many gay men who have been married to women at one point because they felt it was the thing they HAD to do in order to 'fit in' with society. In fact, this is quite common in the midwest, where homosexuality is considered very immoral. If gay marriage were legalized, being gay wouldn't have such a stigma associated with it, and gay men and women would be able to come out of the closet at a much younger age and would be less likely to fall into the 'I have to get married to someone of the opposite gender so I can fit in" trap.
I don't think you can. You either has to be single or married to adopt. Just living together is neither. if you are in a samesex relationship and has gone through partnership might be possible though.
Anyone can do anything they want to as long as they truly want it. No, in Islam having a boyfriend/girlfriend type of relationship is not allowed whether your a male or a female and whether the bf/gf is Muslim or not. If you have anymore questions regarding the matter, just ask and I'll be happy to answer them. i gree in islam having a boyfrnd or a grlfrnd is not allowd but today no youngr generation follows it .....so if a muslim girl personlly like a non muslim boy...then it is not allowd in islam.....u cannot marry him unless he accpts islam...:)