1) pretty much. it's the speed of the link between your laptop and the router, you router then has a separate connection to the internet which should be 50Mb/s
2) despite what others are saying a selection of speed tests to well known speed test sites will give you a good indication of what you are getting, in fact a better indication of real word usage speeds than a test located on your ISPs network, it's the speed you can connect to other machines on the internet that's important, not just the speed you can connect to your ISP. if you use a couple of the better known speed test sites and try at varying times of day you should be able to build a good picture of the real world figures you are getting. A single test may not give a clear picture as there are a lot of other factors that can influence the speed results.
Try
http://www.speedtest.bbmax.co.uk/
And
http://www.broadbandspeedchecker.co.uk/
And if I was you I'd be keeping a very close eye on the upcoming superhub firmware update to make sure you get it.