Depending on the strength of the bolts used and the thickness of the wood base, a 200 pound load should be supported substantially. If your pit is built from brick, you'd have to find another solution.
You customize it with whatever size piece of plywood you buy, so yes it should
There are no real dimensions because you make the plywood to fit your particular situation
you could do that if you want
I had the same problem at first. Have another go at adjusting the levelers. They need to be just off the ground when the caster are engaged (levers down). And you need weight on the base to test it. Try putting one foot on it, pushing down pretty hard and trying to moving it.
They stay locked.
You'd have to contact the seller to determine future marketing.