Would you support Trump as a Third party candidate if Jeb is the Republican nominee?
No.
You’re putting the cart before the horse race.
Trump will be 70 before the election - older than Hillary.
Once all his past positions and donations (inc admiration for the Clintons) are highlighted, Trump will not win the GOP nomination.
If he goes 3rd Party, he will elect Hillary, just like Perot did TWICE for her husband.
I would support Trump if Bush was the nominee.
A 3rd party candidacy will ensure a Hillary victory. So no.