Your connection will only be as fast as the weakest link.

Yeah, but I'm just wondering if my device manager settings are optimal.
Should I be using full duplex?

Everything auto should give you full duplex if your devices support it. Eastlink gives you 5 external IP address with "30" service, so you can just put a switch connected to your cable modem and then a router connected to that for any wireless devices.

I had no problem getting 30down/5up with anything when it was not going through any junk routers.

Internally there is a gigabit connection to the cable modem, so you can hook up a gigabit switch no problem.

a friend of mine just picked up a gigabit switch brand new for 30 bucks - 8 ports and it works great so they aren't expensive at all