3)No 2nd player- you are the only person.
Powerman's suggestion breaks "1) Perfect shuffle luck", and was obviously meant to be humorous. My attempt humor was more subtle.
The real question then: With worst shuffle luck, how many turns does it take to hit 5? My first guess is Scheme/Horse Traders opening... maybe 7?
You HT to hit a hand with two coppers or a silver in it. If you play scheme and HT in one turn, you're guaranteed to have two coppers either this turn or next. So worst shuffle luck should be T3 or T4 HT, then T5 scheme (it doesn't matter as long as scheme comes after HT), topdecking itself twice to hit the HT on the bottom of the deck. HT/Scheme gets 8, which seems suboptimal.
So on the 3/4 split, we can guarantee at most 2 shuffles, though it's just a turn away from being 1 shuffle -- maybe something else is faster. Jack guarantees either having 5 or trashing an estate, maybe that helps?
And of course this is all moot because hitting 5 with HT doesn't let you topdeck 5 treasures...