Hi op
You are doing so well , you really are.
My exh walked out 9 years ago, 22 married. 4 dcs.
He hasn't has contact(his choice) with the dcs for years. We don't even know where he lives.
I , like you, am astonished , thstbsuch an involved "dad" could just leave his kids with out as second glance.
I found it helpful to have a "before" and "after" idea of my exh.
It was impossible to think it was the same man somehow.
These early days are , I won't lie, really hard. But you have years ahead of you with you 5dcs.
That.is.priceless.
And he won't ever , ever have that.
Not like you will , even if they do let him into their lives , he's betrayed them as well, it will never, ever be the same, once trust is gone, it just can't be the same.