nvu

as a test you can just skip it all together and short the connector pins together. the compressor should kick on. its function is pretty basic, too high or too low pressure it'll switch off. it'll short the pins when the pressure is nominal.

it's likely fine, the timing chain tensioner can get sticky, but doesn't fail catastrophically like the timing belt tensioners. those years had the oil consumption issues due to low tension rings from the factory. probably check if your model year is affected and keep an eye on oil levels between changes

oil filter up top is an fb engine, timing chain. they're noisy on startup until the tensioner fills with oil. no need to replace if it doesnt sound bad when warmed up

Check if the cabin heater working. If so the pump is working. Might still be some air trapped in it, try parking at the steepest incline you can and do the radiator fill again.

I only see one wire tapped from the main harness. can you trace blue/pink wire and see if it runs into the ignition switch? guessing it's a breathalyzer module that needs breathing into to start the car.

The suspension gains positive camber really quickly when it's near the end of its travel. Not sure what's causing your too high issue, but the vibrations are likely from the tires gaining positive camber when the suspension bounces up higher than usual.

As long as it doesn't leak it's fine. They are tapered threads so likely the new one has more meat on it and sits higher. Is the 2010 an EJ engine? If so don't worry about cracking the block. The oil galley has a nut with a tapered hole for the sensor. Worst case you only need to replace that nut if the sensor threads get ruined. Random picture, but you see the nut where the pressure switch goes on to.

Likely as a failsafe. If the charge bulb burns out, the alternator would stop charging and there wouldn't be any other way to know until the battery's drained.

The brake indicator is also connected to the alternator. If it's going off and you're sure it's not the fluid/parking switches, the alternator is grounding itself. Either it's bad or there's a short somewhere.

Just occurred to me there's an intake air temp sensor on the maf. The codes are pointing at the maf, did they clear after you plugged it abck in and reset the ecu? On my 2003 impreza, I've had the maf heater wire cook itself brittle before. Cut open the wiring loom and see if any individual wires have discolored. With my case, the car never threw any codes, but the plastic tab was broken off for a while. Only found it after splicing in a new pigtail, the burnt area was about 6" before where there was a cable tie on the loom.

Collapsed hydraulic lifters maybe?

You mentioned a lot of things got crushed in the airbox area, check the plastic piping from maf to throttle body for cracks, etc... check for vacuum leaks too. Did your year come with plastic intake manifolds? That might be suspect too.

Does it start without the maf connected? Try disconnecting battery to clear all maf learning, unplug the maf and keep it disconnected, plug back in the battery and start it. At very least it should start the engine in failsafe limp mode. If it starts again, the problem is likely sensors. If it's not starting then, it's more basic mechanical: fuel, spark, timing...

When the tail end of the transmission jumps up and down, it tilts the engine back and forth. If your rear transmission mount is the oem open style, change it to the solid group n style. If the prev owner already installed it, the pitch stop is sort of redundant. These are probably not the exact ones for your car, they're even different. but you get the idea, look at the rear trans mount and see if they're already solid.

Good point el_freddo, the results won't be accurate. My reasoning would be to rule out any seriously broken parts. With only the compression tester in one hole and the no spark plug in the others. The main idea is to verify each cylinder still has any compression. If one cylinder has bent valves or something broken, the starter wouldn't have much resistance and spin freely. If there's really a 0psi at this point, something is majorly bent, not tightened down, or broken.