It's call "fog"...he is living in it right now...he doesn't know what he wants, what he feels, he is very confused...pretty classic for the MLC'er...
So what to say when he asks "What are you doing?"...I would say "Being a wife as best I can under the circumstances. My vows haven't changed yet."....or you could say "The same thing you are....trying to figure out what is best and see what happens." Don't mention MLC, D, waiting for him to come home, waiting for his return...nothing that puts the attention on him as far as requiring action...act as if you are content where things are...he is only going with the flo because in the fog you can't see very far ahead...
But...and you know this is coming...calling SIL and telling her that you wanted to be there and then mentioning your concern about H wanting you there or not....well not a good move...that is pursuing....of course he is going to say what he did otherwise he looks like a bigger shmuck then he already is!...This also shows him he has power over you because you were afraid of making him mad...so he knows his feelings are controling your actions...
I know you were just having an honest conversation with SIL...but really it is best not to give anyone else words to use in your behalf...her saying to him that you wanted to come but weren't invited by H and you didn't want to make him mad is like having your best friend call you mom to ask you if you can come over after your mom already said "no"...of course this sounds like Jr. High...but this is how H thinks right now...
I know it is hard to sit home when you know he is with family that you enjoy too...and where he has invited you before...but just maybe that night he needed space...
I sat home many many many nights...my H had moved to another town several hours away, I didn't have an address, a phone, nothing....his cell phone was still in my name so I could track him via GPS...I knew he was all over the big city...going to clubs and stuff...what good did that do me???...none...what I am saying is you at least KNEW H was with family...not likely to get into much trouble (other then the drinking which is another classic sign...and one that can lead to a very serios problem now like it did my H)...so next time...busy yourself...play Scrabble with the kids...build your own fire pit and have fires outside with your kids making S'mores or just hanging out...start crocheting, knitting, embroidery...
Don't allow H to tug you along on his journey...one thing if he asks for your company...but when he doesn't...let it go
I know this is so very hard...I was where you are 3 years ago...it does get better and you will deal with things better if you just focus on you...becoming what you need to be in order to be the best mom and wife you can...let him figure his own stuff out...you still need to "find" yourself in all of this....remember?...keep focused
