I know you state that you still love him but by remaining married to him with his behavior as it is you are enabling him to abuse you and your chidlren. Somehow you've got to slap him upside the head and get him to change (Actually God works the change but you have to help).
Filing for divorce may be enough to bring him to his senses. If not, then going through with the divorce may be. There is nothing to stop you two from remarrying if he does come to his senses later and you desire him back (You are under no obligation however as he broke the vows).
I'd recommend filing and taking him for everything he has or ever will have. Likewise file suit against his plaything as she has alienated his affections from you.
(and of course keep praying for him)
We're praying for you
Exactly.