Broadband forum: Bandwidth Speed Extremely Slow

I recently moved and a benefit of where I am living now is that Internet access is free. I share access with my landlord and run it wireless from his router. My connection is good, 4/5 bars and my PC itself has better specs than his laptop does. For me, I have a Intel dual core 3.0ghz Processor, my OS is Windows 7 x64 bit and I have 8gbs of RAM installed. Our ISP is Comcast.
As of late, I've noticed a drastic change of quality when it comes to streaming movies from Netflix. Also, from time to time, I'll stream a video from movies2k.com which, too be honest, is a hub site for pirated videos. As far as I can recall tho, I just started using that site recently, yet my download speeds were slow before that also. So, I have a couple of questions;
1) First, since I run my Internet access off of his network, we should share the same IP, correct?
2) I have taken a number of different speed tests, including one from Comcast and my DL speed averages 3.5mbps while my upload is higher, usually 4.5mbps.
So, the other night I asked my landlord to take Comcast's test also and he received a DL speed of 18.0mbps and an UL speed of 12mbps. I've read about Comcast "Choking" customers bandwidth, however, if they were doing that, shouldn't his PC also be effected and not just mine? Also, now when I go to the "Other" site to stream something, I use a Proxy IP and normally, it plays flawlessly which leads me to believe that that its more my PC that has the issue instead of Comcast "Choking" me. so my next question is, what on my PC could be hindering my DL speed? My primary browser is Firefox altho at times I will use Google Chrome. I've run speed tests on both browsers and Firefox usually gets a better score, but not by much. 3.5mbps compared to 3.10 for Chrome.
Also, I clear my cache and cookies daily as well using a tune up tool that my Anti-Virus (Trend Internet Security Maximum) program provides. I also run a full AV scan daily and my AV software itself I just updated to the newest version and is brand new. No viruses have yet to be found.
So, what in the hell could be causing me to have such a dramatic drop in my bandwidth?
Any help is greatly appreciated!