Some of the adapter ports require the removal of the R12 schrader valve before you install the adapter, some require it be left in, I am guessing that you did or did not do it correctly here.
I am more cheap than you, but after doing A/C work for 15 years, I have to say that you are doing the wrong thing trying to save a bound up compressor. Even if it does work it will self destruct soon, then you will have to deal with the metal that will be pumped into the system. I recomend getting a used compressor that is not bound if you do not want to pay for a rebuilt (wich is first choice).