One problem I just realized and maybe someone can give me guidance,

in the base of the tank where the sump will go, some of the wood is bubbled up from years of wear and tear. It looks as if at some point in time there was some water under there and as a result the bottom is uneven at one or two points.

I was thinking of maybe constructing a base for the 30 gallon sump out of 2x4's to evenly spread out the pressure that is applied to the 30 gallon tank.

Does that sound like it would work? Not sure if I have any other option.