#1
I was wondering anybody who speed picks in style of Zakk Wylde do you rest your picking arm on the body of the les paul or does it float which one will reduce tension.
#2
I've got no idea how ZW picks but usually resting your arm on your guitar reduces stress on your arm. Still a matter of taste of course, if you pick using your whole arm I wouldn't rest my arm on the guitar :p
#3
Ultimately this is a matter of personal taste, both have their benefits. Floating your arm will initially seem much harder, personally I prefer it but many do not. Experiment with both and see what's best for you.

Note though that you have to be really careful when you first attempt floating entirely - if you're not careful and you don't focus on what your shoulder is doing (for example if it hunches up when you move to lower strings), you can get some serious shoulder pain.

While I'd recommend doing stretches before you play regardless, I'd recommend it even more if you're going to try a floating hand. If this sounds like a lot of effort to learn to play floating... then just play with your arm resting on the body. As I said it's a matter of personal preference.
ESP Horizon FR II (EMG) / Ibanez Prestige RG1570 (DiMarzio Crunch Lab & LiquiFire pickups)
#4
The thing you need to do is get the use of learning how a relaxed hand feels like. Then apply that to your playing.

Here is a link to my free ebook.

http://www.guitarlearningtips.org/the-guitar-blueprint-to-success/

Read chapter 2, i showed an exercise there in this matter.