If he has been cashing checks, you are entitled to at least half I'd imagine. I would get as much documentation from CCBill as you can about how much they've paid over the last couple years. If it's a signifigant amount, you definitely should take legal action. Even a small amount you can go to small claims.
The trademark is interesting as well. If you own that you have a right to that domain. The cheapest way is through UDRP.
http://www.icann.org/en/udrp/udrp.htm
It's $1500 for them to review which is much cheaper than some lawyers. If that doesn't work, you can go the lawyer route.
It's tough to give more advice without knowing more about your divorce agreement or business relationship with your ex-husband (who owns what essentially). If it's substantial money on the line, you definitely should sit down with a lawyer and get some advice.