But the question is, what is Michael Myers in this whole ideal? He's not necessarily undead, because he isn't all gross and obviously deformed like Jason is in most of the movies; it could be that we just never really see his skin, but we do see his hands and his eyes, and from those we would say he's not obviously a zombie killing machine like Jason. But he is more or less unstoppable -- he's been just as manhandled as Jason and Freddy, just not in as a supernatural manner.
Michael Myers is always temporarily dispatched by more mundane means, because he is "human." However, his strength and resilience is beyond human -- he's be set on fire, he's been shot and stabbed, thrown off balconies and staircase landings, and possibly even electrocuted (not sure on that one). He could be one of the "fortunate" people who cannot feel pain, but this doesn't explain his amazing healing abilities, because the injuries he sustains don't normally leave much of a mark on him. From what I can remember, he also never shows any obvious impediments from movie to movie, when if he we a mere mortal, he would be horribly crippled by now.
For the class, I think Michael Myers fits right in -- except for the stringent entry requirements, which also exclude Leatherface and Freddy, as the special requirement is written. Also, I don't know if the Slasher necessarily needs to be Undead; none of these are undead: the Fisherman from both I Know What You Did Last Summer movies, the Ghostly Slasher in the Scream trilogy, Michael Myers, and Leatherface from the Texas Chainsaw Massacre movies. I think the special requirement should be worded in a bit more broad a term, such as "Circumstances must have conspired against the Slasher to be in such a way to cause his fractured mental state that makes him eligible for this class, as determined by the GM. Those already involved in the grisly murders of teenagers, family members, or both qualify."