I have no idea if the guy's story is legit, I have never heard of this frame. Even if it's not a Trek, but it's actually titanium, this is a good price in your area. I still haven't gotten my hands on a Ti frame/bike. The frames alone go for several hundred on the low end.
Since I've never ridden a Ti bike I cannot say whether it'll be too whippy for you. But what I CAN tell you is that those early carbon tubed frames (Trek 2500, Epic, et. all) are about the flexiest frames around and I would NOT recommend one for you if you're a clyde. Especially in the larger sizes, they are more flexible and as a result more prone to being torn apart.
If you want a nice stiff frame, you need to get a more modern welded aluminum or one-piece carbon frame. These frames are lighter and stiffer than their early glued ancestors. Modern aluminum frame road bikes can be had relatively cheap these days, a LOT cheaper than that "titanium Trek" in the ad. And they will serve you well.