I ride stuff like that with 38mm tires. The key is to keep the pressure as low as you can get away with, without damaging the rims or getting pinch flats. Find the widest tires you can fit on the bike, and if your rims allow tubeless, get tubeless tires set up. This will allow you to ride with really low tire pressure. The tires will mold around the rocks and gravel rather than ping off them.
BTW congratulations on the weight loss. That is extremely impressive.