Wow Jennie I'm sorry you're feeling such stress and anxiety about this wedding. I agree with the girls above that one of the best things about BDW is that you can vent to unbiased other women, who will support you no matter what. I truly believe that girlfriends are food for the soul
That being said, my advice would be to listen to the fears you're having about his past and ask yourself "why?"....has his past behavior in relationships always been a worry to you, or is all of the added drama with the ex/upcoming wedding of his BF/etc just making you focus on it more? Has he done anything recently that makes you think he hasn't moved on from his shady past? We all have pasts and have made mistakes in relationships, hopefully he's learned from those and is willing to treat you as you deserve.
Unfortunately, the baby mama drama won't go away. You can't change that....but both you and your FI can change your reactions to it. Some women are just hateful and psycho, but that doesn't mean it has to become your issue As far as the co-worker and same salon drama, have you ever thought about switching salons? You certainly don't need to deal with that high-school b.s. day in day out.
Good for you for being so clear about the material things in life not being so important. Sounds like you've got a good head on your shoulders. It does sound from your post that you're bothered by your FI's financial dependence on his family. Will that change after you're married? Will that still be an issue? More importantly, does your FI see it as an issue? Some families are just like that, where the children still are financially dependent on their parents their whole lives. And for some people that works, but it sounds like you may have a different approach. It's okay to let people help you, as long as you're okay with it.
If you're anything like me Jennie, you can easily talk yourself into being stressed out. Yes, I think the questions you have about your FI/his past/his drama/his family are legitimate questions to ask. Yes, I think these issues can be overcome. No, I don't think you need to tackle them all today. What I'm trying to say is, take a deep breath, and let this roll off of your back a bit. A good talk with your FI may be warranted about your anxiety surrounding these issues, and what ways you two can overcome them as a couple. You are not wrong for feeling unsure. You are not wrong for feeling so anxious about all the added stress. It just makes you human. Take care girl and let us know how we can help.