Hoping it's not too late

[MrBond]

"He'd be so much better off if I could step away"

Yes he would.

"...but I just can't - I want him and us too much!"

See that's your problem. You're not thinking about HIS needs. You're only thinking about your own. Stop thinking about yourself and start thinking about him.

Release the chains around him and see if he comes back on his own. Right now you're causing major pressure on him. His GF has the right idea.