As far as Facebook goes and that small bandwidth, I would go into Facebook preference settings and tell it NOT to autoload videos/media. A while back Facebook redesigned their site to where you can scroll down and videos play etc. You will want it set to only playing a video when you select to play it. When they rolled this out it was a royal annoyance. I had plenty of bandwidth so that the page loaded at an ok speed, but i didnt want videos to autoplay when scrolling down. I'd check to see if maybe the videos/media are eating up your bandwidth on page load that is causing for it to lag out. If this is the cause you should be able to easily fix this in preferences and have Facebook load faster.
Additionally on a recent thread I had going here I noticed that Facebook and Youtube have been laggy lately and I found out that Flash is Single-Threaded which I was not aware of it how it executes on CPU. If you have a weak CPU system you could also be dealing with the fact that Flash is single-threaded and slow on a weaker CPU system. My system that showed it the worst was a Netbook with Intel Atom N280 1.66Ghz. I thought my system had an issue because Facebook and Youtube were slow and laggy and my CPU was only using 40-50% CPU utilization. The 40-50% was because the CPU has HT and so while it showed 2 cores, it only had 1 true core and 1 virtual core and so only the true core was in use at 90-100% so the hardware monitor was lying to me about the CPU use.
