You are a perfect example of why one shouldn't ride boards that are too small for their weight. You are 225lbs on a 156 Burton Custom that maxes out at 175lbs.
If you overweight an elevator, bridge, or car... something is going to break. Your 225lbs frame on a 156 Custom is stressing the heck out of the board especially when you go into a press of any sort.
If you want to ride a park board that small, go with something more durable like a bamboo core board such as the K2 Fastplant.
If you want to stick with a Custom, the 163 will be better for your weight. You'll only be 25lbs over the max which won't stress out the board nearly as much as being 50lbs over.
Also consider your height coupled with your weight. You have considerable leverage over a 156 as well as being overweight for it. All signs are pointing to bad board sizing than quality.
Seriously, look into the K2 Fastplant. Bamboo is super durable and I've seen big people try to break it by flexing it to no avail.