Since others say they can use their home servers with FIOS — and I can't see how any responsible individual is going to consider the WHS a business use — then perhaps you just need to start over again by uninstalling the WHS, and if necessary blotting it from the router's memory. How this is done perhaps entails resetting the router using the reset button (with everything unplugged?), powering it down if necessary, and starting cold.
Since you used to have the server connected to a different configuration, for all we know your server configured itself to that ISP's way of doing business somehow. Maybe your server is used to one style of connecting online and that is somehow imprinted in its operating system config. I hope you don't have to do a clean install of your server's OS all over again, but keep it in mind as a last resort, ok?
Btw, granted, you might find the odd testy tech, but should this be construed as Verizon wishing to pull the carpet out from under you for wanting to download your camera's memory card onto your home system while you are on vacation?
As a matter of fact I got similar treatment when I wanted to know how to configure my Actiontec for FTP. I was told to go ask Actiontec. "We don't support that feature". 
I called back and got someone decent who told me how to do it.
I'm sorry about your experience, but since I do not work for Verizon I will not apologize for the actions of the tech in question. Shucks, when I call and tell someone how badly I was treated by someone similar, the usual response is to apologize all over the place, and feel embarrassed.
Most of them are decent human beings, I promise.
