I went ahead and emailed him. I got a very fast response indicating that I can contact the seller, have the seller issue a "call tag", and then have the seller reship the firearms to a different FFL dealer without an excessive wait period. I emailed the seller and am awaiting a response from them.
I also contacted Arnzen Arms as advised by many here. She confirmed that they move forward with transactions after 3 business days but added: "However, in this particular case, I do not think we would be comfortable performing the transfer, knowing that there is still an open-status NICS check existing for the same person/gun." So it sounds like she'd be willing to provide speedy service for any transfer except this one.
So assuming things move smoothly with the original seller and LE gun sales, I am back to square one with selecting an FFL since it appears Arnzen Arms won't work out. Sigfan recommended Southwest Arms too. I will probably contact them next to see if they might impose a waiting period.
I read that the FBI or ATF or whoever runs the computers that are used to process these background checks are constantly being updated and have been causing a lot of false denials / delays lately for people that have never had a delay or denial ever in their life. For anyone reading this thread, I guess the lesson to take from it is do your research on an FFL before you have firearms shipped to him/her. Once the FFL is in possession of your firearms, it is a hassle to unwind the transaction. Don't automatically go with the cheapest guy. Make sure you are aware of their policy regarding a "delay" result from the background check and are comfortable with it. This goes for anyone with a squeaky-clean background as well as people who raised some hell as a young adult, since delays/denials apparently can arise from a questionable background or from a error in the computers that run the background checks.