Hi,
Since the only path for air to get to the barrel is through the valve and valve seat, I expect something is still wrong. From the sound of your initial problem I expect that there was damage done to the receiver block by the hammer (may have been happening for a while and the damage was simply accumulating).
I had this happen to a Crown Mk II I bought used and made the mistake of dry firing to empty the plenum of air when I first got it. I didn't realize that the previous owner had put in a 26g hammer weight and had the internal hammer adjuster maxed out. The aluminum around the hole the valve pin stuck out of was deformed and caused the vale to jam and not seat properly, blowing all of the air out of my rifle. The only solution was to send back to FX USA (at the time) where they redrilled out the valve pin passage.
I expect that your valve pin passage has been damaged and that is what is keeping your new valve pin from properly seating in your new valve seat.
Sorry for the diagnosis! Though if there is a good machine shop near you they can probably use a honing tool to sort out the problem without having to redrill.
Cheers,
Greg
utahairguns.com 
