Start by checking the basics. The engine ground harness should be bolted to the rear of the block, directly under the airbox. There should be a ground strap on the passenger side that usually comes off the car.
0302 and 0303 are adjacent cylinders in the waste firing order. I would lean more towards you having an ignition problem rather than a head problem since 2 and 3 are on different sides of the engine.
Dead Tach/Speedo/Odo are common on Forresters of that GEN. Usually a bad connector joint in the ram assembly. Tach/Speedo/Odo signals are super low impedance digital PIP. Gauges HATE bad signals on Subarus. Start the car and remove the nozzle from the board. If the gauges seem to go in and out, you need a new set.
Subarus are careful when it comes to alternators.
