I think it's time to cut and run. Honestly. What good is it to have a relationship which leaves you unfulfilled? And you've talked about it many, many times, to no avail.

Announce you'll be leaving and set a date. Watch his reaction. If he doesn't do much of anything, then you had NO RELATIONSHIP worth saving anyway.

Nobody is going to live forever. And there's no prize at the end of your life for enduring a crappy marriage. It's time we all start recognizing we won't live to be 150.