That's right, a MAC address usually has numbers as well as letters in it, richgm. I would think that's probably because it's expressed as a hexadecimal rather than a decimal number. An address with numbers only is usually an IP.
There's a couple of ways you can check your actual speed (from the results you post, I'd say yes, you're probably on a 750Kb service because it's consistent, but that's not a certain indication).
One is to check your modem configuration: open your browser and direct it to the IP address for your modem; it varies according to what your modem is, but mine (NTL:250) is
http://192.168.100.1/, and that's fairly common. You'll probably have to enter a password and username; for ntl modems this is often 'root' for both. If you can get in, go to the Configuration page; it should have something like Maximum Downstream Data Rate: 2048000 and Maximum Upstream Data Rate: 200000 if you're on the 2Mb tier.
Alternatively, see the CS article '
How do I check/change my cable modem speed?' for the ntl links where you can check or change your speed.