I've been walking that fine line with my H too. He is adamant that I "get" that he's done. So I always questions myself when it comes to things like compliments or other positive interactions.
I think you SHOULD thank him (loudly!) But Bklyn makes a good point, since he's concerned that you are buying into the D, casually mention a small detail, which lets's him know that it's still on your mind. But then it's safer to applaud him for his efforts with the prom.
(Bklyn usually knows the best things to do in these situations, I just sound like a parrot) But, I wanted to let you know that I appreciate your advice on my posts and I do see similarities with our sitchs.... i don't know if I can drop my rope yet- right now it's wrapped around my waist for extra leverage!
M-31, H-31 T-9, M-7 S-6, s-20mth sep 8/1/11 ILYNILWY 11/29/11 Creating separation papers. Discover H has feelings for BFF, she does too 1/11/12 H moves out 1.20.12