I’m not sure the mod podge would seal the wood in the way you are hoping for . Even with a few layers of mod podge, I think the teeth marks will still reach the wood underneath. Is he chewing on furniture legs, baseboards? You could try rubbing a bit of white vinegar on the furniture he is chewing on (the smell might dissuade him) – it’s safe to use around buns, and won’t mess up the wood.

How much out of cage time does he get?

Buns are natural chewers, and some buns chew on things more than others. Destructive chewing could also be due to either illness, hormones, or boredom. If you decide to get him neutered when he is old enough, destructive chewing is more likely to subside than if he is not neutered, though there is always a chance that this might not change. While it might not be boredom since you provide him cage-free time and a lot of toys, it would be better for him if he could have more cage-free time. Three hours is a good start, but definitely try increasing that time. Also, buns are social animals, so make sure you give him plenty of human interaction during his play time and all other times.

If the furniture is in a consolidated area, you could block off the area with a gate or a diy gate with c&c grids. Or, if the furniture is scattered about, you could try taking some cardboard and wrapping it around the legs of the furniture. If he continues to go after the furniture, when he does, try to distract him right away by gently scooting him away from the area – granted, you might have to do this many times before/if he gives up. Hope this helps .