those bikes appear to have a more significant rear wheel weighting than your average bike. Go whole hog with a custom build and 13g spokes. 14g should be strong enough for a regular bike but I'm thinking of 275lbs coming off of a curb sitting on the seat and not on the pedals. Your weight and the bikes design require more attention on the rear wheel than a simple out of the box assembly. The wheel should have been checked out at time of sale and immediately in the first few weeks of riding. Even then it may not have been sufficient over a years use. I wouldn't bother with more spokes given the 26" rims,just put in some big spokes and have a custom rebuild.