M20M pilot reported experiencing a rapid accumulation of unexpected icing despite icing equipment and reported other equipment failures; which resulted in deviation.

Narrative

Departed ZZZ2 under VFR and a 4100 ft. ceiling with the intention to climb to FL 230 while presumably still north of forecast icing south and east of ZZZ1. This was all to occur before turning east on course; by then well above the forecast icing of between 6000 and 20000 ft. in the area south and east of ZZZ1. While I filed to overfly ZZZ then ZZZ3; ATC cleared a route to the south; which I rejected with clearance delivery as too close to the airmet boundries. They instead agreed to have me overfly ZZZ4 then ZZZZZ; which likely made no difference in my overall judgement error and outcome. Climbing through 5000 I noted light rime building on the leading edges and windscreen. Pitot heat was on before becoming IMC and I activated weeping wing; defrost and windscreen deice. At the same time the Autopilot had malfunctioned and not engaged either heading or navigation modes and repeated cycling of its power toggle failed to achieve navigation capture. Further; I inadvertently extended the speed brakes while level at 6000 with too brick hand movements and when I noticed I found they had frozen extended and asymmetrically and could not be retracted. I asked ATC for an immediate climb above 10000; the reported tops; but they could not due to conflicting ZZZ1 traffic. I then [requested priority handling] and asked for an immediate descent and nearest airport landing which they gave me. With the brakes out; the windscreen obscured and no Autopilot to lean on; I nearly lost control. I focused on keeping wings level; small turns to maintain direction and a gentle descent; no more than 500 fpm. Upon breaking out at 2500 I was in VMC and had an otherwise uneventful arrival at ZZZ5. Tower cleared me to their Runway XX but Runway X was straight ahead and I queried them on final and landing was approved; any runway. After arrival at the FBO there was still rime ice on small areas of the leading edges and the speed brakes which eventually retracted as the ice melted. Lessons learned: icing forecasts are not geographically exact; flight into known icing capability may not save one's life; avoid rapid hand movements that could extend speed brakes at a bad time; delay departure until icing forecasts are well away from climb to cruise altitude.