You must have gotten the wrong impression from the Clyde forum, there are only a few racers in there. The majority of them (us) are either recreational/fitness riders or commuters.
I'll go ahead and give you some clyde advice here though, but I suggest you should restart this thread in the Clydesdale forum to get more input.
Any non-department store bike will work for your situation. The bikes themselves are just about all the same when it comes to holding your (our) weight. I am checking in at 292lbs right now, down from over 360lbs from over a year ago.
The biggest concern for you will be the wheels. Settle for nothing less than 36 spokes for the rear wheel and 32 spokes for the front wheel. However, the more the better. Back when I was 360lbs I had a rear wheel built for me with 36 spokes to replace the 32 spoke wheel that came on my bike. It is still holding strong after over 5000 miles of commuting and many many offroad adventures.
Your next concern, and just as major as the wheels, is the "fit" of the bike. Please go to a bike shop and make sure that they fit you properly for a bike.
After that you'll be working on getting the perfect saddle. There's a good chance that the one which comes with your bike will work out fine, but if after a month or so you are still sore in the ass you might want to upgrade. And you'll get plenty of info from the Clyde guys about saddles too.
Now comes to your riding style. You say you want to ride around your complex as well as hit some dirt trails. This is fine but know that knobby tires for offroad use are a major drag on the pavement. If the dirt trails you plan on riding on are hard packed dirt and/or covered in gravel you can get away with getting only one set of tires that will do it all, the Kenda Kross Plus comes to mind, I used those tires for the exact purpose you have mentioned and they worked out great! I actually wore them completely out and had fun doing it. This will save you from having to have two sets of tires (one for the road and one for the dirt).
The bike that I got a couple of years ago is the Giant Rainier, which has suited me well and still gets ridden like hell. Granted you don't have to spend as much as I did, I'm just letting you know what another clyde has used who has done exactly what you plan on doing.
Just remember, the rear wheel and the fit of the bike are more important to us heavier fellows than anything else on the bike, assuming the bike comes equipped with decent components, which damned near every bike you get from a bike shop will have.
I hope I have been of some help to you.