Many of the answers to this are in the sous vide index http://forums.egullet.org/topic/136274-sous-vide-index/ You can overcook with sous vide, its just harder. Leave stuff in tooooo long and it'll get mushy or dried out depending on the temp and the meat. I'd take it out and refrigerate till serving if more than a few hours are involved. SV units reheat food nicely. Nitrate curing eliminates most if not all C. botulinum spores, so cured meat is safer than uncured in this respect, but why press your luck?