2013 WRX missed shift - 2nd Gear at 80mph

By my estimation that puts it at around 8500rpm.

It threw a check engine light that was for a camshaft timing sensor but nothing else.

It seemed to drive okay and idled fine but there was a sort of clicking sound that would start in the mid rev range. It was worst when giving it just a little throttle but was less with more throttle and went away with no throttle. It still had normal power as well. The part that threw me off was I have a new aluminum skid plate that can sometimes make noise so I had stopped on an on ramp to take a look and when I rattled it around by hand it sounded exactly like it so I figured that had come loose somehow and was vibrating to some resonant frequency. I also looked to see if there was any oil on the engine or any weird sounds when idling but it sounded fine, engine temp was okay.

Another 5-10 minutes down the road I noticed I was losing power. I reset my trip odo to get an mpg reading and was getting half of what I should be, around 14.5 at 65mph instead of 28-30. Before I could get to the next exit to pull over the temp gauge suddenly shot up and as I was approaching the off ramp the engine shut off. Pulled over and opened the hood and the coolant was boiling over. I let it cool down for a while and then tried starting it once but it really struggled so I assume it's seized in some fashion. I didn't try again. Oil was pretty low but was still on the dipstick.

I had a friend with me so we pushed the car into a gas station and it's currently sitting there overnight. My dad is picking it up with a flatbed tomorrow.

Based on this info what other basic things should I check for before presenting it to a shop? I'm guessing there's serious damage that's been done but I don't know what, maybe a bent valve? Probably also a bunch of warped shit from overheating since it's an aluminum block.

I've had this car for 12 years now and I don't really have the 10k sitting around to afford an engine replacement or another car to drive. I'm not super mechanically minded and it's almost entirely stock just with a Cobb bypass valve and a brand new intake tube between the intercooler and throttle body. Annoyingly in the many years I've had this I've done this shifting into second accidentally once or twice before but never this severe.

I'm shaking from the stress and not really thinking clearly so sorry if this is a bit of a mess. Thank you for any thoughts you can offer.