I think you might be onto something with Cloud, because my don't starve steam cloud folder is gone now. I don't have any current saves at the moment though, after I lost my last one. a) It's enabled. b) It disappeared. c) It simply behaved like I had never created the character. d) No. e) 1 f) Like I said, it's not there. h) Yes, and I had the problem in Torchlight 2 once.
Just lost my game around 70. Put in a ton of hours yesterday, log on this morning and it's all gone. Terrible bug and I feel like it's not being paid enough attention. It essentially renders all my progress null and void. Didn't even get the god damn progress to that third character.