I myself have not had to replace the fabric or any other part of this wagon, I have taken it apart and washed it after using it to carry groceries, I would find a seamstress and see if that person has some canvas and maybe that might help.
Looks like 1/4-20 unc
Haven't used it on steps yet. I assume it should work fairly well with the pneumatic tires.
Take one of the bolts with you to the hardware store and ask for assistance, Mine kept coming loose so I replaced the wing nuts with locking nut and now no more problems.
YES DEFINITELY, I put 3 cases of water and $75.00 worth of groceries in mine.
Yes it is, just line it with plastic so you don't get stuff stuck in the bottom of the wagon, especially if you have children that ride in it or use it. Just makes it easier to keep clean.
I remember measuring, it is about 19 wide and 27 long
No. It's heavier than most wagons and the tires don't roll well on sand. However, excellent on all hard surfaces and great on grass.
Weight not sure, but as for rolling it while folded up is easy, I roll mine around my apartment all the time while folded up.