You need medical extension orders so Fort Sam can cut your retirement orders. Push your PEBLO/MSC to escalate officially, and request written denial from S1/USARC if they won’t act—that usually gets movement.
Your VA comp is effective 1 April 2025 (the month after retirement). If VA finishes your rating in April, you’ll be paid 1 May. If not, you’ll get paid later with back pay to 1 April.