I believe I would start by dropping your rideplate to about 2 degrees above keel.
To me, your low speed porpoise and bowrise would be indicitative of the rideplate being too high. (allowing the boat to "rock" back and forth from the hull to the rideplate.)
I don't think your 2 degree wedge in your droop is going to cause any of your problems mentioned other than possibly the steering problem. It could be that with the droop you are now dragging your divirter. (?) With the divirter on there, you should be able to overcome/adjust past any thrust angle problem.
Good luck, I'm sure someone who is a little smarter than I will chime in.
Ken F