If you like the idea of a road bike but are concerned about durability and comfort at your weight, consider a cyclocross, gravel or touring bike. They all are similar to road bikes but tend to be beefier with more relaxed geometry. Another advantage is that you can mount tires larger than 700x28c which will reduce the chance of pinch flats and decrease road vibration. There are lots of them out there in steel, aluminum, carbon fiber and even Ti. I started at about your weight and am still a Clyde. My personal preference is good quality butted chrome-moly frames. Modern steel frames can be surprisingly light, very durable, and more easily repairable than other materials. I also really like the feel/comfort of a good steel frame.
I strongly suggest working with a LBS as fit and setup have a huge impact on comfort. One size fits all bikes from big box retailers are a real crap shoot in regards to fit and there are no options for swapping out parts to increase your comfort and control. For example, a bike shop would usually be willing to make adjustments like a change in the stem length/angle or swapping a straight for a setback seatpost for a minimal charge to make sure a bike fit you right.
Don't be scared of "road" bikes either as there is a pretty large variety of bikes that fall in this category. There are extremely aggressive road bikes out there but there are also endurance and comfort geometries available. Frame failure is unlikely unless you go with something ultra-light, but you might have to address the wheels. Entry level or low spoke count wheels can prove problematic for a large rider. My suggestion is usually to just make sure the stock wheels are 32 spokes or more and to get them properly trued and tensioned by the shop. Catastrophic failure is rare, more commonly a wheel will keep coming out of true and/or start breaking spokes. If that is the case, you will have to look at a more durable wheelset. Like I said, I'm a big guy and I have a butted chrome moly frame with CF fork road bike that has an endurance (less aggressive) geometry. It does have upgraded wheels, but I wouldn't have hesitated to ride this bike stock at your weight.
As far as the Trek 820, in your original post you stated that you were thinking of a road bike. The 820 is a decent, entry level mountain bike, but a road bike it is not. With slick tires it might make an OK commuter but you don't need the suspension for riding on paved surfaces. The modern 820 is a far cry from the 820 of the 1980s and 90s which was a rigid (no suspension) chome moly bike that made a great commuter, still not a road bike though. If you like the flat handlebars there are flat bar road bikes or hybrids that lean toward road bike styling.
Last edited by GravelMN; 03-19-15 at 02:49 AM.