my wrists are crap as well, so yeah I just cross my arms and set the bar on my upper chest and front delts. I don't have a problem with any pain on the front delts like this (but then again I'm only using a couple plates for weight, not going very heavy).
idk, maybe try using the pad. or just try high bar with the bar on your neck/traps, but set yourself up so the weight is leveraged to the front (which is easy to do on a smith machine , not so easy with a traditional barbell).
as for the big difference in reps . well with the leg press I'm trying to pump everything up and force a bunch of blood. so I hit 20 reps.
with the smith front squats its all about the time under tension, deep stretch, and contraction. I go super slow. I go ass to the floor. I pause at the bottom. then I push slowly back up. I only hit about 8 reps because after that my form will break down and I'll begin using to much core and lower back to push the weight (which I don't want at all at this point)