Friendship advice/suggestion needed.

So as clear as I can explain. Ever since I got with my fiancé his best friend hated me. He pre-judged me. He made the first year of our relationship difficult for my fiancé. They have not been best friends for a year. I have had to tolerate a lot of abuse from his ex bf and his partner. The is no reasoning for it. I believe it was jealousy. He does not have a practical? Relationship. He dumps on his girlfriend and daughter when ever he feels like it and expects his friends to do the same. I absolutely believe you should make time for your friends but he wanted my fiancé all weekend to himself which sucks because my fiancé works very long shifts I barely get to see him myself. So time has to be fair. There's a lot more nasty stuff to this story. I hate that my fiancé doesn't have his friend but I understand why he ended there friendship. I know he did it because he was sad to see me me so hurt all the time. They recently tried to mend things but it went south because he denied anything happened. He said he's never had a problem with me but it's not true as he's always gone out of his way to make me feel like shit. Fast forward to today and we found out that it's looking like he has brain cancer. I feel a guilt. I shouldn't because I've always been nice to him but you don't want that kind of thing to happen to anyone. Especially since he has a little girl. We absolutely care about him and I can't help but want to be supportive. Should I myself try to build bridges? All I ever wanted was a sorry. Nothing more nothing less. Should I message him explain everything that he should just be honest with things so we can move forward? It's just one of those terrible situations. He may be so poorly but can you just brush everything under the carpet or do I deserve a tad bit of respect. Or forget about it all. Just move on and get along. We just bought a house and are finally getting out of our one room and I want him to come over and chill with my fiancé and game like they used too. Sorry if I make no sense it's hard to put 2 years in to all this.