It does not look like a shed to me, it looks like a coronavirus mask storage and other life essential protection quarantine (outside of the main dwelling) decontamination space.
Coronavirus trumps HOA... if you think of it that way.
As for the deficiencies in construction I did not actually read your post... but simply put, the building is so tiny and the roof load is so miniscule there could not possibly be a concern structurally. Finish out any way you like... if it goes asunder... so what.
Strong winds in certain parts of Colorado could move the building. I doubt it weigh 600 pounds. You might want to consider that.
