Gen 5 – Cylinder 5 Misfire, Oily plug, possible PCV and how do I know if I have done long term damage

I have a 2015 Outback 3.6r with 197,000km on it that has always consumed a little oil. The past 6 months though that consumption increased to approximately 1l per 5000km. Last week while driving up a mountain pass that vehicle had some hard shudders and the dash lit up, I read a code P0305. I was able to get the car back home and upon removal of the spark plug from the 5th cylinder I could see that is was covered in oil and in a sorry state. I replaced this plug and also the ignition coil, (full disclosure, I replaced all plugs and coils) as it looked to be in poor condition too, put everything back together and…..I still get the P0305.

The car at idle has a very noticeable vibration to it with dash lights indicating a fault, but once it hits about 2500 rpm it totally smoothes out and all dash lights disappear. In reading other posts on here overnight I think I may have a PCV valve issue and I plan to investigate that today.

My asks, if it does turn out to be the PCV issue will correcting this fix my misfire problem? Have I potentially done some more significant damage to the car by not addressing this sooner? Lastly, are there other areas and potential causes I should be investigating? With living in a small rural community the opportunity to take it to a mechanic is not readily available and I am hoping this can be a home shop fix

Thank you all for reading, any help or guidance that can be offered will be appreciated!

Ian