Single engine small aircraft pilot reported a trim and auto pilot malfunction.

Narrative

Departed ZZZ with light winds and clear skies. I had performed autopilot test as part of checklist and it was nominal. Reset trims to neutral. Applied sidestick pressure to disconnect servo but no luck. Continued and completed preflight. Upon departure; the nose pitched down in reaction to the low nose down trim settings. No manual trim control wheel in the aircraft. Recycled the red trim disconnect button; nothing. Recycled both autopilot disconnect switches; no help. Pulled elevator trim breaker and reset; nothing. Hat switch continued to be unusable. Slowed the plane as slow as practical. Hand flew the airplane with maximum trim down attitude. [Advised ATC] to ZZZ1 and landed Rwy XX; no assistance required. My arms were close to exhaustion limit from pulling sidestick aft and trying to initiate power and flap changes. I don't think I could have lasted another ten minutes. I will be examining the trim circuit; including all switches. Once issue is identified; will repair or replace parts as needed.