Awkward situation

So me and my partner of 6 years (with a break up in between due to him being diagnosed with an illness and having a mini break down) are finally getting married!!
There's just one problem, his mum really doesn't like me and is very fake towards me and his sister in law has openly told me just what his mother says! His brother follows suit of his mother and his dad I just love. Well they're no longer talking to my partners sister who I'm really good friends with for absolutely stupid reasons to the point where they haven't congratulated her on her pregnancy..
There's more! We've had a tight month as I've started a new job and my pay date has changed so we borrowed £100 for his dad which we'll pay back next week just for my partners brother to have a go at him despite him and his wife borrowing money to pay their £250 mortgage despite them both working! My partner also suggested they go and look at suits in the next couple of weeks as he's his best man, his brother replied with 'yeah guess we could...' 
All of these issues are seriously putting a bad spell on our excitement for our wedding to the point where we argued about it last night as after a month of him saying he didn't want them there and be persuading him otherwise because at the end of they they are his family, I agreed with him and he went crazy at me?!
I don't know what to do😞😞