Advice on new pfsense build for high jitter isp (RF Link)

joshuaeb09

Hello Guys and thanks in advanced for the help.
Please stay with me as this is sort of a long post.

Current Situation/problem:

A client/friend of mine lives in a rural area and the only high speed he can get is RF via the water tower close to his house.
The connection speed and base line latency isn't to bad around 4.5 mbps* and 110 ms* to the nearest metro area (me). Packet loss is also pretty good about 5%* over a 4 hour test period. Unfortunately the jitter is around 35 - 55 ms* which appears to be causing some problems with PC gaming (WoW and COD MW2) and XBL. Another issue is that he gets a 10.x.x.x private IP from his service provider.

Problems :

When we are playing XBL it appears that his router(Crappy belkin from walmart) is closing sessions whenever his jitter gets to high. Causing private chat to drop, black screens in Halo, etc.
His NAT is only open whenever his Xbox is connected directly to the ISP. Same with the PC (Windows Live Messenger, COD MW2, etc.) I am assuming that is ISP is using UPnP to open ports.
Router also appears to be closing HTTP and FTP sessions when ever he is trying to download large files like drivers and whatnot. Once again I'm thinking that the jitter is playing a large part in this.
Most of these issues are minimized when connected directly to the ISP

My Solution (Please advise) :

Will be building a pfsense 1.2.3 box at his request, mainly because as soon as I changed my state table optimization to conservative his end was the only side terminating connections.
Specs : p3 1.0 GHz, 384 mb RAM, 2 D link Fast Ethernet NIC's - PC he had lying around. Stress tested and confirmed working.

Proposed Pfsense Config:

Static DHCP lease for 360 and Gaming PC
Static Port NAT configured for said IP's
UPnP enabled
State Table Optimization: Either Conservative or High Latency ? Not sure on this one.

My Questions/Concerns :

Is it possible to have the UPnP requests translated through the Pfsense box to his ISP's router?
Will Pfsense's state-table optimization help him at all?
Line test were done with PC connected directly to the ISP at multiple times and to multiple speed test sites/locations.
Behind the Belkin Router these test do not change much except for when there is load on the line. Jitter increases but only when using the Belkin router.

Thanks guys for any help.

–Josh