Finally spilling the beans…
I think you’re kidding yourself about a few things and hopefully you haven’t become too invested in him — but the best way to get him to come back leShem Shamayim is to have your Rabbi handle it. And if he comes back and resents you for it and can’t get over it t’ll be a korban you gave for Hashem and be a great zechus for you to find YOUR RIGHT SHIDDUCH as obviously it wasn’t meant to be.
But if he’s this perfect boy and comes back to live a perfectly religious life he’d be THANKFUL YOU BROUGHT HIM BACK AND NOT HOLD IT AGAINST YOU!
Again, I can’t stress enough how much you are blinded from seeing the truth so please discuss your feelings about him with someone competent.