I have heard, although I do not know if it is PF or player-created, that vitoxin, being a retrovirus, and affecting DNA, cannot be cured by cloning except where the clone has been created from genetic samples taken before the vitoxin was administered.
In re: drug addiction, addicts of contemporary drugs of addiction talk of feeling the desire for the drug long, long after being 'clean'. I'm not aware of any studies on whether the changes to neural pathways ever 'change back' after a period without drug use (given the brain changes daily throughout life). However, I don't think it's controversial to propose that substance dependency has a psychological as well as physiological component - and that would, I would think, survive cloning unless something 'went wrong' with the brain scan to change personality in some way (IIRC the cloning company website that was put up as a promo for Eve a while ago had the likelihood of personality changes in the 'legal disclaimer).
As for mental illness, I have a vague recollection that the TCMCs were originally designed to cure mental illnesses? Can anyone remember anything about that?