If you want to try to keep that grub screw from working loose, try putting some teflon pipe tape on it. should fill up the gap and make it tigher for you. if the blade is curving when you tighten the T bolt, your over tightening it. It doesnt' require as much pressure as you think to hold the blades, if your using proper tension. If it's cutting on an angle, then I still think the table is not square to the blade. Perhaps the square your using got bent at some point? What do you use to square the blade, and how do you do it?
I have 2" square I use on my Dewalt. My Dewalt has it's own issues that I can't seem to correct, but doesn't seem to affect my cuts much. I can square the blade to the table, with the arms all the way up. If I place a straight edge touching the blade, when I lower the arms, the blade moves about the thickness of a #7 blade to the side. I've tried adjusting the set screws on the clamps every which way, but to keep the blade touching a straight edge all the time, my table can't be square to the blade. Doesn't really seem to affect most of my work, but I'm sure if I was to do some very fine pieces it would prob cause too much sideways vibration and snap a piece.
But I used to over tighten my blades in teh beginning.. then I figured out what a good amount was.. Now it's more when i feel the set screw touch the blade, I do a like 1/5th to 1/4 of a turn and that's it. Never had the issue again, except on maybe a couple 2/0 blades when cutting maple and i needed to tighten more to get more tension.