Ah, good questions, Grey.

Yes, it's touch range, however, I don't see why you can't utilize your spear for this spell, mainly to keep you out of range.
Heightened learning happens on a crit roll, and lasts for a while after that. (you'd roll again to see how much you gain, with a 20 being the full 50%).
1d20% would be from current HP, so, diminishing, and it would happen after the afflicted party attacks, or moves.