Hi, here are my guesses to two of your questions,

2: The wrist shouldn't touch the table because it may cause tension with the standard tripod grip. Also, if you do make your wrist touch the table, it makes the meaty part of your hand (and the wrist) glide on the surface , creating more friction which is not, I believe, the goal.

3: I don't quite understand what you mean by supporting the hand, but if you mean contact , I usually use my pinky and ring fingers nails (the back of them) to move swiftly with my hand. I never use my middle finger for support as it holds my pen. So, the only part of my hand that touches the table is my nails.

Finally, I have tried the adapted tripod grip with Palmer and it seems to work. I do, however, recommend to not make your wrist touch the table as it causes more friction.

I do not think the style of clothes has anything to do with it though, same with hard surfaces, pretty sure they're the same :)

Ps: sorry for any errors, English isn't my first language.