1. How much items can i store in the body?
(I tested putting 3000 weight on the body and it still is able to run and follow me... is this forever)

2. Is the only way to give the Dead Thrall weapons is to kill it... and place items in its dead body

3. How do i make amour and stuff as equipped items on the dead thrall
(I killed vampire... put enchanted clothing on it... and it reverts back to a normal mage robe... and doesn't use my power enchants... and it was naked)

4. Is there a npc that doesnt moan like a zombie that gets annoying

you can put as much weight on thralls as you want, and dead thralls are extremely selective with their items, they only wear what they were wearing when they died (not sure if this applies to followers, because i think they just wear their default stuff.
there is a small list of thralls who dont moan and groan like a zombie, and i remember cicero is on that list of about 10-ish people

Does anyone know the list?

Didn't find the list at quick glance on UESPWiki and Google search, but a guy called Malkoran at least doesn't groan while being thralled.

Astrid dosn't say anything when she is a thrall.