Looking for ways to intentionally reduce wireless bandwidth

Greetings. I haven't posted on here in a while, so I'm not positive if this is the correct subforum for this. I apologize if it isn't. My situation is thus: I have the cliche roommate hogging the bandwidth, and unfortunatly he has the router and modem in his room as well. I am looking for ways of subtly reducing his bandwidth. I can still admin into the router via the web-based tool, and he'd be none the wiser, but I cannot put my own DHCP between the router and modem, and the router has no advanced QoS support. And its a crappy Ehome Eh100 router, too.

My main angle here is this: He's on wireless, and I'm plugged in via one of the ethernet ports.

I have, from the web setup tool, the ability to modify the following settings of the wireless functionality:

Transmission rate (1MBps being the lowest)
Signal strength (In %'s, down to 12.5%)
Beacon interval (from 20 to 1000, default is 100)
RTS threshold (from 256 to 2346, default is 2346)
Fragmentation (from 1500 to 2346, default is 2346)
DTIM interval (from 1 to 255, with a default of 1)

It also has the standard long/short preamble selection, CTS mode choices of none/always/auto, and WMM enabled/disabled (claims to be some form of QoS but I see no way of actually managing this further).

At first the signal strength and TX rate seem like the obvious choices, but perhaps a little too obvious. There is also the downside of having his computer no more then a few feet from the wireless router.

So, within these parameters, what would be the best way to limit his bandwidth? Will dropping the fragmentation threshold only clog up the wireless traffic, or the whole router's?

Thanks in advance for any tips, and sorry again if this was the wrong subforum.

Edit: Oh, and before anyone comments on just talking to the roommate first...theres 3 of us and I'm the odd man out with 2 brothers. They've also been renting the place for a while, and they couldn't care less.