I want to address the tank purging issue.
Many new tanks come pre-purged, meaning that they have been evacuated. The two 20lb tanks I purchased at Costco (less than $30 each) did not require purging.
Rather than dump a full tank of propane, I suggest that you go to Costco, Sam's Club, Home Depot/Lowes, Ace/TrueValue/Murdochs, or wherever you choose and just buy a new tank. If it says purging is NOT required, you MUST resist the temptation to open the valve, or you will introduce air into the tank. If it is not prepurged, just ask the propane attendant to do so. It's an easy process; they will charge you a bit for doing it since they waste a small amount of propane in the purging process.
I'm somewhat skeptical that your problem is a result of not purging the tank, although it's possible. Since you have replaced the regulator, it seems much more likely that the orifice needs to be cleaned. How to do that has been covered repeatedly on this as well as the other forum.