To answer your last question about riding years on end and still be over 200 pounds is real simple...it's called genetics. That is NOT saying your genetics is inferior to someone weighing 160 pounds and riding for years on end, just different that's all plain and simple. If you've gone to a doctor and he says you need to lose weight then ok, but how much weight are you to lose? If you've been trying to lose say 40 pounds because the doctor said so for the last couple of years and you've been unsuccessful then you need to ask the doctor about a diet and what to change in your physical exercise. Larger people are built to be muscular, so maybe going to a gym every other day and riding your bike every other day when your not at the gym will build up muscle mass. In some aspects I envy you, because when I was young I tried like crazy for years to put on muscle mass and it failed, I was that skinny guy that girls instead looked at the more muscle bound guys. So don't let your weight depress you, you were made like that so you need to work with it. I knew a guy who had large bones but he weighed a lot, or so he thought so, so he virtually starved himself to the brink of death with very little fat on him and he still weighed 185 pounds, though he did drop 80 pounds he looked horrible, and it wasn't till he was admitted to the hospital that he discovered he wasn't suppose to be that thin for a person 6' 4" with large bones, the doc told him his idea weight should be 215 to 220 pounds. So your idea of a weight problem may not be one at all, so go see a doctor and find out the truth and then ask what changes you need to make to reduce if that's what the doctor says you must do.
Wheel wise, usually lower costing wheels are more stout because they are heavier and built to be stout. ROL makes a nice set of wheels for heavy riders called the Volant R/T and they're only $525 for the pair; see:
https://store.rolwheels.com/volant-rt-alloy-clincher-p148.aspx the recommended rider weight max is 240 pounds. If you weigh more than 240 pounds you may need to go with a custom built wheel using Velocity Deep V Clydesdale wheel and opting for 36 spokes front and 40 rear; see:
http://www.velocityusa.com/product/wheels/clydesdale/deep-v-clydesdale-wheelset These are actually less expensive than the ROL so you might want to consider only the Velocity if you need to save a bit of money. On that Velocity site the wheel weight they list I'm sure are for the wheels with the least amount of spokes and not for the set with the middle amount or the most amount of spokes.
Are there other wheels out there? Of course but I didn't have time to list a bunch but those, especially the Velocity, are a great set of wheels for a very reasonable price. they're not racing wheels they are wheels designed to take a heavier person banging on rough city streets without fail or constant truing.