sounds like you`ve got most of the answers already. produce a slope to central area andpump it out. putting down 6mil plastic and spreading an inch or so of gravel over it helps also. make sure u have proper ventilation underneath the house. vents should have a net area of no less than one foot for each 150sq.ft. of subfloor area with the wood to ground clearances being no less than 12 inches to bottom of joists. these are bare ground clearances. you shouldn`t have to move the house. good luck and no worries mate.