MIL and Husband Rant

Hannah
I'm looking for advice to help my husband. 
About two weeks ago, my MIL called my husband (in tears, and not happy tears), telling him that she's engaged to be married. My husband was quite upset. He was happy for her, but he didn't even know she was seeing anyone. Not to mention this guy hadn't asked him, the oldest son, about asking his mother to marry him. We, my husband and I, didn't even find out the guy's name until the next day when we were looking at our Facebook pages. He talked to his mother for a long time about it. She promised him she wouldn't rush getting married (she told him they were looking at June), and that she would bring the guy around the family (she'd never brought him around before (again, we didn't even know his name)). She told him she had to post something on Facebook, because this guy's daughters started posting things about the engagement, and she wanted her family to find out from her instead of them (totally valid point, but that's how all of my husband's siblings found out about the engagement at all, was from Facebook). But that excuse clearly says that this guy has brought her around his family, yet she hasn't brought him around her family. 
My MIL texts my husband this past Thursday "Hi sweety. Just wanted to let you know we're going down to get married. Love, mommy." My husband was absolutely furious. To sum up his emotions, he feels orphaned. His dad is awful, so they don't talk, and now his mom has run off to get married, and moved several states away, with some guy that he knows absolutely nothing about. He knows his mom is very much the sort of woman whose self esteem is determined by her relationship status, but she's only been seeing this guy one-on-one for three weeks! She's known him since only October, and has been dating him, as well as another guy at the same time, since mid November. She split up with the second guy less than a week before getting engaged to this new one. 
I hate seeing my husband so upset. He refuses to talk to his mom about it, because he feels like she's made a horrible mistake (he says constantly how you can't know someone after knowing them for only a couple months). She has no plan to bring this guy around her family, and now my husband feels the need to step in for his younger siblings again (his sister is super pregnant with her first, and one of his brothers is starting his first semester of college in a week). Is there anything I can do to try and help him try to move on from this? I know he and his mother will never have the same relationship because of this. But still. I've tried taking him to his favorite restaurants, given him full days to himself, gone to see his types of movies...I'm just lost for what else to do. He cried two nights in a row (something I've never seen him do) because of this. Any advice is welcome.