1: S28-150s are used by many a US Heavyweight(albeit mainly the lesser-known ones).

2: I took the idea from Jack Orr's CrOoKeD eVo's stats:

Weapon: A Co2 full pressure flipper at 750psi with 1 110mm ram,and a 2kg bottle and a 750g buffer tank.
3: To quote something Leo said earlier in this thread about Armox:

You can't drill it, you can't weld it, the only thing you could do is clamp it in something, but that thing would probably get ripped off before the plate gets a scratch.
Apparently, Armox is very tough, perfect for a robot...