Redw

By the way you are a smart woman for not filing as soon as possible, watched his behavior and didn't let your emotions dive you. I applaud you for the that. 

You done the right thing. Since he came on K1 visa, his residency will be approved only if he applied with you. He can go and get married to 100 women, and he will still be denied. 
My advice: divorce him, move on and let him regret what he has done. You being worried about it won't help you at all. Don't fall for him again, do you to be happy. 
At this point he will have to get out the country, restart the process and IF he get approved than he will be able to come again.
Good luck. 

Since he entered on a K-1 visa he can only get his residency/greencard through the original petitioner - that would be you. He can marry this new woman all he wants after you get a divorce but he can't adjust his status through her, he needs to go back to his own country and start a new visa process from there. He has no legal way to stay legally in the US at this point.

divorce.  take care of urself.  immigration his problem not ur.  what happen to him after divorce not ur problem.

As others said, he's no longer your problem.
 
He can't remain in the US without you even with a new spouse, and it will be hard to show a bona fide marriage with anybody else in the US if they tried to get a new visa (plus there would be a 10 year bar to overcome as well).

You can't control other people and their actions.  Just move forward, and seek your own happiness.  Let him wallow in the sea of legal problems ahead.....
 
Good Luck....