1) kinda. it depends, if you have a cable or dsl, then you wont notice the difference. but if you have dailup, well, i think it might.

2) it is normal for speed but computer speed and down speed, that kinda didnt make sense at all. 4 host that is normal, most of the host tend to up about 20KB each. sometime hosts MAXIMUM their KB which is not good, it could bottleneck the ISP server. then the ISP will noticed you using a p2p and can kick you out of their ISP or block the port

3)there is some people that will answer that, it been posted many time, take your time to look around, use the search feature