I think you just have to realize that a change in eating habits is needed. I still play but as I said in the other thread, I refuse to get fat to make some coach happy.
But, having said that, I know I can get "away" with more during the season as far as cheat meals go. I mean, I play both sides, pretty much ever snap, so I'd imagine some calories are burned there.
Basically, keep up your lifting and non-lifting workouts. For a guy your size, you'd be surprised how much of an impact walking every day for 30-45 mins will have. You won't get ripped in 4 weeks, but over the course of a year, it adds up. Dr. Lowery wrote about this once.
From personal experience...I did listen to my coach freshman year of college and ate too much, got fat but hit a certian number (I think I was up to 315 @ 6'1). I was disgusted tho...slower, and felt like shit. So I changed schools and decided to lose the weight..over the course of a few months I got down to 260 and the speed came back. I'm not gonna get confused for a contest Bodybuilder, but haha it was a huge improvement.
My High School OL coach was the same way...he was pushin 300 at about 5'9. After college he lost around 65lbs...nothing big, just workin out, cutting out the junk other than an occasional cheat meal.
So my advice? Remember that at 250lbs you'll still be pretty damn big...because I know some lineman get used to that feeling of being one of the "big men." Lose it slowly, and steadily and understand you will fuck up sometimes and eat a cake, a 1/2gallon of ben and jerry's, and a dozen Dunken donuts. Don't freak, just get right back into the diet and training.