I load a variety of bullets between 130 gr. and 150 gr. with H4831 in 7mm RM. H4831 should do fine, though your velocity is not going to be up in the typical 7 mag. neighborhood, but in my experience, accuracy can certainly be attained.
I have loads with some 139's, 140's, and 145's that range from 58.0 gr. to 64.5 gr.. I've found that with that weight range bullet, starting some where around 57.0 grs. is probably going to save you some time and components, there no real need to start at 55.0 grs. with this powder / bullet combo.
As for what's going to be the accurate charge, and oal, it's going to take some work up to find the most accurate.
GS