You're not going to get proper DHCP information like this, at least the way I'm currently understanding it:
MBA -> Thunderbolt/FW800 adaptor -> FW cable -> Mac Pro
One of these ends will have to offer a DHCP service (and have static info) to have the other get DHCP info. Usually DHCP is used in a much different type of network for slightly different purposes. This kind of "ad-hoc" setup is exactly what self-assigned addresses were actually for (provided internet access is not an issue).
In this kind of setup, two computers who are told to get DHCP addresses will not get them, and usually this is not a problem if the two computers just fall back to a automatic self-assigned IP addresses. (Broadcast packets, bonjour traffic, etc work fine most of the time onder this arrangement.)
I would imagine then, that the Thunderbolt/FW800 adaptor or the config for it is somehow at fault. Wrestling to get this to work may eventually produce results, but there's got to be a simpler solution for you at this point...
Typically when someone puts together a complex scenario of configurations to make something they:
A.) Leave directions, a sort of road map of what they did, so that in the event it stops working you can quickly retrace your steps to get it back to work.
B.) Provide a method to contact them in the event that it stops working.
So after 18 hours of troubleshooting, and 7 different technicians working with you on the issue in store, you've come to an Internet forum to ask for help instead of just going back to the location that got it setup for you? Seems odd... but with that out of the way.
As BigBlue stated, one machine needs to serve DHCP in order for the other machine to receive DHCP. If you're using DHCP then you can't have a static IP address, the "D" in DHCP stands for dynamic after all, as in... it's always changing. So which computer has the static IP address information and which one is set to DHCP?
Secondly, what is the flow of data here? Are you looking to move data from the MacBook Air to the Mac Pro, or Pro to Air, or regular movement of data in both directions? Thirdly, is there a particular reason why you're using Thunderbolt to FireWire instead of Ethernet? The Thunderbolt to Ethernet connector is 10/100/1000 connection now and Gigabit Ethernet would move the data faster.
You indicate that you have a MacBook Pro that connects to the Mac Pro via FireWire without any issues. Is it implied that it's connected via the same Thunderbolt -> FireWire method? Because if it's FW to FW the relationship is not the same and that information is excluded from your initial remarks. If this MacBook Pro is connected via Thunderbolt -> FireWire how is it configured? Are those settings replicated? If not, why not? If so, how so?
Regrettably, because all of us here are "new" to the issue you'll need to give us some back story on the previous 18 hours.