If you are sure that the compression is really low then the way to go is to open up the engine to see what is really going on. It's possible a valve job would make things ok. I think their price is low If they are doing the work of taking off and replacing the head. I would want to think about the overall condition of the car before doing this.

Did you have the trouble codes read, which may be very informative. Ignoring the compression readings, your symptoms are consistent with fuel pressure way too high (bad regulator) which is not a difficult problem. Sounds like you have an internal engine problem but you should eliminate all the simpler possibilities first.

I would personally not put any kind of substances other than fuel in a fuel system. Even injector cleaners have very strong solvent properties and should be used infrequently if at all.