I think I would need to look through the AFM and the WB manuals to form a definite opinion. The trimsheet data should be fine as the only envelope changes will be truncations etc. in the envelope to accommodate the error analysis.
My best guess at this stage is that the answer to the first question would end up being just a matter of following the forward limit up to the higher weight .. by moving aft, the limit permits a higher weight ....
regards....