#1 - Could this be related to #4? You might be breathing a little hard on the rudder causing the climb. If not, you could always move the CG forward just a little to see what it changes.
#4 - I'd mix the rudder to the throttle. I don't remember what radio you are using, but it more than likely has a high/low throttle auto rate for the rudder as one of the options.
#6 - You might want to consider going to less throw instead of disconnecting the lower ailerons. I would expect your rolls to barrel a bit trying to use just the top wing ailerons.

Ahh, the joys of trimming a new design

John