DECLARATION: I have never used an 'EFB'
Right, with that out of the closet:-
RTOW is NOT affected by estimated or actual TOW so why you have a need to enter such I cannot fathom. If you really do have to, then I assume ANY number will do to get the EFB to proceed to the next step
RTOW IS affected by fuel burn, so there MUST be somewhere that you enter this to compute?
Rarely, I suggest, would you need to 'fiddle' with engine thrust settings?