1) Yes, Pillar Men are weak to hamon, just like flames can be extinguished by water, but that doesn't mean that you can extinguish a house fire with a bucket of water. Ceasar and Jospeh (who mind you, was already able to do pretty crazy crap with hamon), still were only able to superficially damage the Pillar Men before training. So no, the avarage hamon user can't even defeat a fully developed Vampire, let alone a Pillar Man. Joseph at this point, is only able to do a weaker version of his Overdrive, which is deifinitely even weaker than what he displayed against Straizo.
2) Stand Users don't have Non-Physical interactions, they can just see Stands, not touch them, and you don't even need it to overpower a incorporeal being with sheer strenght: You can't possibly tell me that
Danny Phantom as an intangible can restrain
Son Goku just because the former is non-corporeal. You can still overpower an intangible force. Hermit Purple itself has no feats above Tier 9, and Dio, a very weakened vampire, casually overpowered it with his own strenght before Joseph could even channel hamon through it. Dio mocked Hermit Purple's lack fo power for a reason. Now imagine Kars, someone who is leagues above Dio in terms of raw strenght, getting grabbed by something as weak as Hermit Purple.
3) Experience is the only thing Joseph has going for him here. He has too weak of a ripple, and no Sun to defeat kars since the fight takes place at night by SBA. And about the range part, yes, Joseph has a range advantage, but that won't help him much because Kars' bone blade doesn't have a low range either.
4) I have no idea what kind of trick Joseph can come up with before getting bodieed by Kars. He ain't winning this fight by sheer intelligence or experience.