that he'd messed up too much and too many times, that he'd hurt my family and me for too long.
That's a bit harsh - although he may deserve that. Mostly I mean the family part. Who gives about your family...they aren't married to him. Your mom treated him badly, too. Does it matter who was first?
Who knows...maybe your mom has been giving him messages like 'get away from my daughter' or something during the last month. It shouldn't matter, though, because your love/R is only between the two of you.
You are probably very hurt. Me having finally felt love for my W, only to have her ask about a separation 3x in 3weeks has got me way down. Just be careful to make everything a calm response, not a reaction from the emotional side of your brain.