By $1, there should be a certain # where at all levels the $0.50 to win is +EV. Of course based on amount you'd get for winning, table share, etc. This # comes from chance of hitting vs. the amount you win. This has nothing to do with the stakes of the gamne or your win rate at the game.
ie: JP will be hit every X number of hands therefore # of hands * $0.50 = amount jp needs to be to be +EV.
The math of this is simlar to
http://www.math.sfu.ca/~alspach/comp29/
Or this one:
http://www.math.sfu.ca/~alspach/comp46.pdf
Now of course there is the rare instance where someone folds the 1 hand that would have made it. But, just the strait odds would probably be enough to answer question #1.
So, all this leads me to:
If we assume his math to be accurate:
We have a 1 in 155 000 chance of hitting it.
So, 155000 * $0.50 = $77500 for a $0.50 jackpot chance to be an even chance.