How can I determine my eventual balding pattern and rate of hair loss? My hair specialist says this is not possible.

You do a HAIRCHECK test and repeat it every year. The first test will define the baseline, and depending upon your treatment or the progression of the hair loss, changes in the HAIRCHECK test will answer these questions. See here for an example: https://baldingblog.com/19-year-old-parent-told-not-balding-according-haircheck/