Questions about tanks

Can a 4 gpm 4,000 psi machine run off a 200 gallon gravity fed water tank? Or should I always use a pump?

yes it can

I have a 4 and 4 directdrive that pulls from my 225, I only have the Hudson float set at about 70 gallons. No problem.

Yes it can.

I cant get my Hudson Float valve to work.
If i tight it too much water dont fliw through, if it too loose it falls