Okay so, before I get into this, know that when I first got engaged and we talked to our parents about how we were planning a smaller wedding so we could afford a honeymoon, my parents and his parents both offered to contribute. My parents are pretty much picking up half the tab (which I love, gotta say, huge weight off my shoulders). His mother is giving us 100 a month (so sweet of her to offer) and his dad offered 20 a month, (which was totally fine).
Later he had a huge fight with my fiance about how it was completely irresponsible for us to get married when we are students and only working part time (we've been together for 10 years, saved up, and although our jobs are technically part time we are both working 35 hours a week) and how he was selfish for even expecting any kind of money out of him (which he definitely didn't). My fiance let fly a whole bunch of pent up rage he had left over from issues with his father from the past (Such as moving to a different city when my fiance was a month away from HS graduation and just expecting him to find somewhere to live, and later moving to another state without thinking about my FI's little sister who barely sees her dad as it is)
So after a bit of time passed they started to talk again and my FI just decided he was going to let it go, even though the things his dad said were really really mean, he decided it wasn't worth it. They didn't talk a lot but they did try to chat sometimes. We invited him to everything, even though we knew he wasn't going to come because we wanted him to feel involved. (My FI was really sad when we had the food tasting though because his dad is a chef and he always dreamed of him coming to the tasting with him so he could offer his opinion)
Now, just recently, his sister came over to hang out with us after spending a week or two at her dad's. She told my FI that her dad had said to her that we are irresponsible children and he can't believe we are going through with this poorly planned "white" wedding (really not sure what that means) when we are so fiscally irresponsible and he's sure it will fail. I have no idea what he is talking about, we are both very financially smart about this entire thing. We planned this wedding with only our contribution in mind so that if something happens to my parents contribution or his mom we can still afford it (although maybe a honeymoon in the states instead). The entire thing shouldn't cost more then a few thousand, which is really good in my area, and we have our head screwed on really straight about priorities. It's really upsetting to me and my fiance that he's still bad mouthing us after FI extended an olive branch and tried to work past the cruel things he said.
Another thing is, my FI and I have been together since 8th grade. His mother was really jealous of me because he's the youngest boy and she feared I'd take him away (she'd say really mean things to me, a little 13 year old innocent kid about dressing like a slut or being a stuck up bitch.... yeah not a very sane woman) but I was relatively close with his dad. The same is true with FI. He loves his mom a lot but he can't get over how she treated me for the first 4 years of our relationship (she's a lot better now) and he was always really close to his dad for his first 18 years. It's getting so bad right now that I don't know if his dad is even going to show up at the wedding and I really don't want my love to have his heart broken like that.
TL;DR? Father in Law is bad mouthing us and the wedding and now I'm concerned that he won't go. Is there anything I can do to help?