Clinton - 384, ~48% of the PV
Trump - 154*, ~40% of the PV
Mystery Man - 0*, ~8% of the PV
*give or take a faithless elector (or two).
Third Party Mystery Man (woman?) is a Generic R neoconservative hack dredged up from probably either the military or the business world. This (Dole 1996 levels) is their ceiling. Their best state is probably Utah, where they get like ~25% of the vote. Despite a lot of beltway hype, they never get above 15% or so in national polling in time for the debates, and thus are never invited. Still, it throws off Trump's momentum and the Republican Party looks like a divided mess going into the election, which hurts Trump's message. Disgruntled 'true conservatives' and moderate heroes eventually vote for this person or stay home, handing the election to Hillary.
Ultimately though, I agree with others here who say that they wouldn't need get nationwide ballot access. If this is a real plan that's getting off the ground, their #NeverTrump general election candidate will probably just camp out in Mormon Country and try to win UT, ID, and WY - to either elect Hillary in an even more embarrassing fashion for Trump, or as part of a sad and pathetic attempt at sending the election to the House.