Sorry to hear the situation is so bad for you! This is a classic example of an IT cowboy...
Unfortunately as the others have stated there isn't a lot we can do for you.
My personal opinion for you is to have a serious talk with him about it...
The only other pieces of advice I can give you is if your computer is a Desktop PC and you are using wireless check your wireless signal isn't weak. This can cause the issues that you are experiencing as well as pages not loading or connections dropping.
Check to see if your computer is set with a static IP address, details on how to do this are found easily on Google. If the address is static, try changing the last number of your IP address to somewhere in the 180-240 range and try browsing the net then.
If this does not work....
I am guessing by the fact that he takes the computer away before you can sign on is because he has some kind of MAC filtering implemented the network too, so spoofing your MAC address will likely not allow you to access the network at all. If you want to try this, Google is your friend. The reason he takes the machine away could also be that he has disabled the SSID from being broadcast and has to enter this information manually.
As others have suggested getting your own 3G or 4G connection may be your only option, but this is expensive.