It seems to me that a lot of guys who were athletes when they were younger do struggle later; I think maybe it came easy in their youth, but not later in life. I've watched my most athletic brother, in particular, give up on athletics entirely because he was no longer dominant. IMHO, you may need to forget about your athletic past; it's just not too relevant and may be holding you back.

Unless you're jumping curbs or bunny hopping sticks, a strong well built wheel should take your weight with no issues. IMO 36 spokes is the way to go for a strong commuter wheel. My tandem regularly carried 400 pounds, handled the power of two people, and never had a single wheel issue. Radial lacing is for weight weenies and their race bike; go with 3 cross for strength.

Grit is what eats drivelines, not weight or power. Commuting can introduce a lot of grit, and it sounds like your commute does. Clean in frequently.

Older used rigid mountain bikes can usually be had for fairly cheap, and are built. Finding one your size will take some time, but that might be the best way to get a strong, quality bike on a budget. Cleaning, lubricating, and flat repair should be the only common maintenance task.