Sorry for all of this you’re struggling with, @beleroy, very frustrating for you, I’m sure. I will say that swapping out the cog for a regular cassette is fairly simple, and usually only requires a wrench and a cassette tool (which are specific to brand and cassette size, but not that expensive.) - maybe a chain whip. No more than $20-30 US would give you all you need.
There are any number of youtube videos or instructions on how to swap a cog and cassette - many from Zwift specifically:
Just imagine this, but in reverse.
Wish you the best, and hope you get things sorted out soon to your liking so you can hit the (virtual) road.