It's cool that you're interested in this stuff, and you certainly know a fair bit already.
Firstly, starting with a VPS is definitely a great start, and quite a few colo providers will do you space in a shared rack by the U, or a lockable quarter rack, rather than jumping straight in with a half rack.
1) As mentioned, this depends entirely on the servers. Many providers will allow you 100mbps burst on a Fast Ethernet connection, and bill you using 95th percentile - look that up and try to understand how it works. If you want <1TB a month to begin with, you can often buy an allowance in GB, as I imagine you do with your VPS.
2) You can either do this with a rate-limiting managed switch or a managed router. Some firewalls will also include this functionality.
3) Have a look around at colo provider's websites, for example www.ohtele.com
4) The IP registry for Europe is RIPE, not ARIN, but again, unless you need at least a /22 you're best off getting them from the colocation or bandwidth provider.
Good luck! And write a business plan - it's for your benefit as well as the bank's.