My H's indiscretions weren't monetary, and he seems better with money than most. But then again, anything is possible. A separation agreement would legally protect me, but my H has severe attachment/abandonment issues and I think it is pretty clear that he is never going to sign anything. I've been trying to get him to sign for 2.5 years now. It is more of a running joke than anything at this point. I could have stopped him from dismissing the divorce, but it wasn't going anywhere and was costing me a lot of money to have calls with my lawyer over what to do about his stalling and various stalking activities. He missed the first hard date in the case and we were both going to get sanctioned for it. I think he'd had something of an awakening by then, and he seemed to be really struggling. He was doing some crazy stuff for a while.
My youngest child is 15 and really wants and needs a relationship with his dad. Since he's been coming to see my son, my son is visibly calmer and happier. It also seems to be settling my H down. I don't really have to deal with him, so it isn't that big a deal to me. I'm stuck in place for a little over two years until my son graduates from high school, so I will give him some more time to sort himself out before I push to sell the house and other things that would impact my ability to do what I want in my life.
I don't think telling your children the truth (especially older children) is a bad thing. I think had you lied to them and then they found you did (even to protect your H), you could risk the loss of their trust and respect. It is up to him to fix the relationship with his sons.
Wow, planning out the next 20 years. That is a little daunting. I have a good amount of retirement that mine can't touch and he gives me lots of money now. I'm self employed so I also save a lot by staying on his medical plan. I can retire in another 10 years and live off my retirement. I'm just trying to make sure that my kids are set by the time that happens.
