My previous post has been updated.
Yes. Forcing a hard shutdown (or reset) is never a safe option. Instead, REISUB/REISUO would have been a better option.
From a closer look at your general description, it seems that forcing a shutdown may have been the culprit in this case.
From the information you’ve provided, the previous assessment seems accurate, and a fresh install is likely the best way forward.
Why you apparently can no longer boot the USB installer I can’t say with any certainty, but my guess would be the USB subsystem isn’t yet able to initialise because of whatever damage has been done.
However, if you happen to have a DVD drive installed, perhaps you can write the ISO to DVD, and that might still boot.
Beyond that, I have nothing more to suggest at this time.
Regards.