1. A lot of ya'll are jumping on the "its theft" bandwagon, and don't understand the definition of theft often excludes making a voluntary payment (as did the OP) While it may not be theft, it may be conversion. Or as in many of these situations, ATF and local PD will tell you its a civil matter.....LE doesn't do civil.
2. Seller cannot legally ship the firearm until he has a copy of the receiving dealers FFL. That is federal law.
3. I'm starting to understand the sellers frustration with the OP based on his ability to explain the situation.
4. If seller doesn't understand credit/debit card usage, including chargebacks, he shouldn't be buying guns using them:
5. "I'm asking if anyone can give me advice on what to do next. I've gotten some good tidbits from a few people on here, so I appreciate that."
No one has given you "tidbits", but actual steps you should have taken immediately....like contact the bank that issued your credit card.
6. Filing charges, filing lawsuits, pressing charges...........silly. Not silly? Calling the darned bank and telling them "I want a chargeback because I didn't get what I paid for".
Needless drama that didn't need to be.