I am in your same age range, I'm also 6' tall, and I went from 305 to 245 pounds through bicycling and substituting some better foods for junk foods. It can be done, and you can do it. The important thing is to find a repeatable, livable routine that works for you. For me, it was switching to bicycle commuting to get to work every day (6 miles each way). I found I actually love doing it and it was better for me than car commuting for many reasons. I eventually gave my car to charity and went 100% bike commuter. That approach is certainly not for everybody, but for me, the repeatability locks me into guaranteed miles.
If you can get the same repeatability by finding a trail or a road route that you can ride daily, or several times per week, you could achieve the same fitness goal.
Riding on streets with traffic can be done safely if you ride defensively and smartly. Before I started bicycle commuting, I read a book on urban cycling that was really helpful to me in knowing how to minimize risks and be as safe as possible. The Art of Urban Cycling by Robert Hurst, if a book on the subject might interest you:
http://www.amazon.com/The-Art-Urban-...+urban+cycling
Over half the battle is route selection. If you decide to ride in traffic, you want to pick streets that are:
- wider lane widths
- lower speed limits
- lower traffic volumes
Hurst does a great job laying that out in his book. He uses the term "traffic intensity" to combine the lane widths, traffic speeds, traffic volumes, etc. You want lower traffic intensity routes if at all possible.
I don't have vision issues like you describe, but I don't think that's a disqualifier. Factor it into your consideration of routes and approaches. I think there is a sub-forum here for cycling with disabilities... not sure if they cover vision there, but that might be worth looking into. Also, the Commuting sub-forum here is a great source of info that is well-populated by folks who cycle city streets every day to and from work.
Sorry for the long post, but I wanted to encourage you and give you a couple resources that might help. Losing the 60 pounds has significantly improved my quality of life in many ways, and I wish the same for you. Hopefully you can find a good cycling route there in DFW that works for you. At least you shouldn't need studded winter tires like I do here in Illinois.