I am sure you are getting a lot of advice, and from a lot of different angles. All I can offer is what I remember from when my marriage was in a similar situation. When *I* was in a similar situation.
DH is not uncaring, he is not blase'. The big thing I learned, and it was in a book about anger and forgiveness, is that this is the beginning of the death of a relationship. He has been hurt. He was tired of hurting. So to protect himself, he pulled back. Anger, betrayal, it shifted to a disassociation. It was to survive. The problem is it goes from that to denial, to REALLY not caring. Then one day he can wake up and go, 'You know what? I stopped caring a long time ago, why am I here?' Right now, it's a scab, covering a lot of hurt. You have to poke at it, and let out all that bad feelings and deal with them. Or they will heal over and then it won't be a front anymore, it will be too late, he will have pulled back to protect himself so far, that he really doesn't care. Don't let it get there. That was my wake up call.
This, is the hardest part. Believe me I know that. I'm a freaking depressive, with bi polar, disassociative, schizotypal disorder. Just waking up is hard, this next part, was like impossible! But necessary.
On anything! So far I haven't seen any follow through and I'm pretty sure Matt hasn't either. I mean, we aren't in your life so who knows, but there's always a reason, a justification, to change things. A negotiation. Going to have more family time, EXCEPT this one time. Going to break all contact, well except for replies to this or that, but no physical contact! Going to take time off of work and JUST be home, well okay part time because I'd just be bored anyway.
I know all the reasons make sense, but the point is there is NOTHING I have seen you write here that you need to do, or will do, that you have. It always gets negotiated down. Honestly, like a drug addict. Well any sort of addict. That has to be contributing to problems with Matt and honestly why he still shows no emotion. You don't follow through on things you say you are going to do. You tell him "No no, I'm doing A. You're right, therapist is right, I just need to do it!" Then a little while later, "Welllllll, A isn't totally necessary. I'm going to do B instead. I know it's not A, but you know it's not G either! So I think it's a good compromise!" Then he just nods. Honestly, probably defeated, because he knew there would be no way you were going to follow through.
Again, I'm saying this from what I read, and knowing now that when I did the same thing I was just causing more and more damage.
Me: Late 30s pansexual poly.
DH: My husband of 19 yrs and father of 3 teen girls.
DC: LDR of +4 year