Let me get this straight: you got divorced, left the JWs, moved across the country to a (presumably) whole new life, where you've now had new sexual partners and/or relationships, and you're worried about making sure your EX-husband doesn't have the congregation's permission to remarry because you think he's a jerk?
Perhaps the question shouldn't be: "does he have scriptural grounds to remarry if nobody finds out I've slept with someone?"
but rather: "where can I find a good counselor who will help me not to waste anymore time trying to punish someone I've already removed from my life?"