First, welcome to our wacky world, sorry you have to be here.
Congratulations on being so smart as to not beg, plead, argue, etc. You are wise and fortunate and way ahead of the game in that regard.
You've received good advice already and I'll just add a couple of comments. If you want to save your M, then you may want to retract your petition for D. Additionally, if you want to save your M the "right" way, meaning he changes and straightens up, you may be in for a long, long wait if your H is truly experiencing MLC. OTOH, if you want to start working on your self, and taking a "wait-and- see" attitude about your M, you just might have a good chance.
personally, I would definitely go for dinner, I would be absolutely delighted if my H had asked me for dinner in the last 18 months. I wouldn't be sucked into talking about the M, if he talks, you can just listen and validate. However, as someone else posted, don't expect anything, and don't be too surpised if he withdraws, or gets cocky, or even nasty, afterwards.
