It seems like a lot of your problems are coming from your own body issues and being concerned with what your family thinks. Yes, it's okay to want to gain weight. Yes, it's okay to want to lose weight. Yes, it's okay to still be attracted to weight gain or watching your significant other get fat. Yes, it's perfectly normal and healthy to explore your sexuality and yes, you will probably realize some things that might surprise you.
The only real obstacle between you and what you want is acceptance. You need to accept that these things are all okay, that you're not a hypocrite, and it's okay to deviate from 'normal' vanilla form. You also have to accept that it's okay to agree to disagree, and that you cannot allow what other people want or expect of you to control your life or interfere with your personal happiness. You can't be afraid of what people will think or say, otherwise you are a slave to that ideal and you're feeding into it. You have to accept yourself for who you really are.
My advice: just say '*** it'. Out loud. Literally, just say '*** it' and adopt that attitude. You can be thin, fat, tall, short, etc; you will never fit into some kind of perfect mold, you will never be everybody's cup of tea. You owe it to yourself to find some peace with who you really are.
With that said (and at the risk of sounding a little harsh) you also owe it to your partner to not project your body issues onto him. I think it's true that we can't really extend unconditional love beyond ourselves unless we start WITH ourselves. If you have a hard time accepting your own weight and fat acceptance in general I think it's natural he's probably feeling some type of way about it, too. I'm very, very far from a relationship expert but I think that the obvious answer is to sit down with one another and hash it out. You can find a way to support one another while you work on your personal issues.
Good luck to you