Something else to consider, once you have the problem worked out, is to replace just the rear tire with the next larger size and save the existing rear for a spare.

Personally, at your weight (I'm 240) 23mm tires have to be pumped up so "rock hard" that they are harsh and tougher on wheels.
IF your roads are as rough as you say, go to 28mm if they'll clear.
That gives you a bit more "squish" factor and go a long way to cushioning a bone jarring ride.

I tried 23mm on the front of my hybrid and the rough textured pavement was very hand numbing. Going to 25mm were just so much nicer. Because they are more comfortable, I'm faster overall. I'm not having to stop and massage my hands.