I have a rather ragged entry door that is going to be replaced as part of a kitchen remodel. Its not a prehung door, but i am replacing it with one. I've already removed the exterior trim to verfy rough opening and jamb size. The jamb seems to be 5 7/16. I can get custom widths down to 1/16 of an inch. Should i go with 5 7/16, or would it make sense to round it up to 5 1/2"? Being an old house i'm not sure about any irregularities around the opening, but if that extra 1/16 makes it stand proud, i can shave some off. On the other hand, if it 1/16" short, i imagine a thin bead of caulk would make it disappear. Any thoughts?

My other question is, if i removed the factory brick molding, would i have to remove the interior casing to install the door? I am trying to avoid removing and potentially damaging the interior trim. I plan on reinstalling the exterior trim/casing as well, so it seems removing the factory brick mold should allow me to shim and insulat all the areas around the rought opening i would need to. Does this sound doable?