One at a time!!! 1)installing a french drain will take hydrostatic pressure off a basement wall--How so? By diverting "some" water from top 2 or 3 ' from wall? Sorry,doesn`t work that way..what about the rest of the wall? Most basement walls are 6-10' deep..so..there is still dirt/clay and possibly tree roots against the other 4-7' of the wall!! Even if you were lucky enough to divert all "Surface" water away,water is still below ground in the soil and it "wicks" underground..all the time! So,hydrostatic pressure is still highly probable,it makes me laugh to keep hearing on home imp. radio shows or news articles that anyone can"divert" all water away from the 'entire wall' by means of Any "Topography" as G. Haege likes to say.Roots from trees or large bushes are also likely to help push/crack a wall..I never seem to hear the 'Whole' story about waterproofing etc..just what they want you to hear.I`ve seen builders/homeowners/whoever install french drains under new driveways-patios and 'sometimes' not too long in the future there is a collapse or wash out underneath due to trying to divert running water underground.No way I would do that to my house...but go ahead,its your house,do whatever you like.