RCJon is right.

If you have setup your equipment in the plane to balance it on the CG as the instructions say, you dont need to mess with thrust. The firewall should have had the propoer thrust built in.
You just need to adjust the linkage to get the elevator linkage right, you probably started with a little up elevator at neutral trim. Turn the radio on and see where your elevator is at with the elevator trim as far down as it will go, just like it was after the last flight you mentioned. If it is straight with the stabilizer (neutral elevator) you probably started out with the linkage in the wrong place. Leave everything on and move the trim to center and then adjust the linkage by shortening the pushrod to put the elevator back where it was with all the trim in after you finished flying. That way when you take off the plane will fly just like it did the last time you flew, but you will have trim control again.

A trainer should fly hands off at mid throttle, but will climb a little at at full throttle.