You"re blaming yourself and I certainly don"t wish to make you feel worse, but the real lesson that could be taken is: Don"t drop down in the middle of a technical manual and start twisting bolts -- begin at the beginning.
You stated twice in prior posts that the manuals were "cryptic," but they"re actually straightforward. Both the Ford and I&T FO20 SOS sections begin with a description of how it functions followed by troubleshooting and adjustments. Then begins complete disassembly/overhaul followed by reassembly.
There was no spring pressure against the interlock cover so there was no need of "releasing the Band 2 adjusting screw per manual instructions" as you did. That indicates you were in disassembly/overhaul instead of the adjustment section, and is what I meant by starting in the middle of a technical description. I cautioned twice about losing a strut or struts - "SOL at that point, etc."
As I understand it, there were problems with the transmission when you got the tractor, so somebody may have been there before you. A few years ago, a guy asked here about SOS problems in a tractor he was looking at to buy. The owner told him that he had "yanked out that screw trying to fix it" (as he pointed to a band adjusting screw).