Better is assing static IP na basement router DHCP for upper MAC address.
Then just disable DHCP on upper router and connect basement with upper with eth cable on LAN ports on both.
Note: You can use WAN port on upper but then upper network will be different segment and computers will not see...
Hm, I have my wired network at home Cat5 together with power cables 230V in floors even with heating tubes and 100MBps goes without any issue in all rooms.
I'm using Win7 as file server, setup sharing files and printers for local network and I can map them on notebook running WinXP without problem. It should work, only between Win7-Win7 it is much easy to setup (don't have to provide user credentials if I'm correct).
If they are IP cameras it exists lot of software to manage them. They has to be connected to the network, even through public internet and that you can connect to each from you computer and then u can used them.
Yeas, 1mbps should be fine, more important is stability and latency of connection.
I think you can start from 1mbps and if not enough then upgrade to 8mbps anytime, depends from your ISP.
Try to check with somebody who has the same connection the ping to playing server, less latency in...
Try disable N on your Belkin USB it seems that Toshiba G WiFi is mucha better then your Belkin N USB dongle.
This shows that N WiFi is not a winning solution all the time.
Bridge - your virtual machines behave as another computer on the network where hosting system is. As the end if you have 1 hosting + 3 virtual you will end up with 4 system on that network.
Host only - virtual machones can communicate between each other and with hosting system but not outside...
I'm using Avira AntiVir Rescue System which is an bootable ISO with antivirus, just boot from it and clean the system. It is actually some Linux based. It has also different functions like browsing drive and so on.