Can you slide the tab to the left (or right - i forgot which way)?
Probably not, since it can't on my 2000 FCWs...

Back to the original problem: how does the camera behave with the back off the camera?
You see, i'm beginning to believe my original thoughts were, uhm... let's say 'misguided'. The back's status indicator not returning to white could of course be the camera's fault after all. If it doesn't transport the film, it will not change the indicator... Stupid of me.

For some reason i had the idea in my had that if the magazine's mechanism got stuck, it would block the camera's wind crank.
And it will, if stuck the right way. But it's not the only possible cause. Why i jumped to that "100%" certainty belief i can only explain as an instance of accute stupidity.

Your thoughts about the shutter not withdrawing being a sign that the camera is at fault are correct.
I thought it might perhaps be because the feeler tab was in the retraction-feature's "off" position, but the 2000 FCWs i know don't have that option. Only the 2000 FC/M had.

So perhaps another new battery after all?
Sorry for all this!