Back when I was flying a little (pre 9/11), trying to carry-on everything for the trip was most of the problem.
It's funny to see a guy sitting there with his laptop case and laptop trying to squeeze-in "work". For most flights, you only have about 1-2 hours max of time you can work.
I'm 6-3, 300+ and flew coach. I never had big problems.
That's surprising. My son is the same size as you and hates to fly because of the hassle. He has to ask for a seat belt extension, and is not allowed to sit in the escape row. Why? I don't know. He has to lift the seat arms because the seats are so small. He never flys alone. Will only fly with me or my husband so that we can lift the arm rests. I always plan far enough ahead that I can get the 2 seat configuration. Forget the local small jets which fly out of our smaller city in Texas. I think the seat size is about 16". We measured them one time. I'm 5'2" and weigh about 140 Lbs, and I just about fit.
I once asked a Pilot as I was leaving a plane when they are going to have us stand up for the entire flight strapped to a back board. this way they could get another 50 people on board. He said he thought someone had already suggested it.
My husband is 6'4" and normal weight for his size. He absolutely hates to fly. He usually sits there with his knees around his ears. He can't fit in those seats either. He also will get the person who believes it's their God given right to fly the whole trip with their head in your lap. BTW their names are both Brian.