So I have set up my remote as per MCE and it is working great.
Glad to hear
1) How do I make it so when I click on the MCE button on the remote MediaPortal opens?
There is a simple plugin, MPtray:
MEDIAPORTAL - free media center - MPTray
Just download, unpack it in \program files\team mediaportal\mediaportal\ and run the BAT file "mptray_install.bat". Run it in a command prompt, within Mediaportal directory (just to see for any error).
You'll find then "mptray.exe" in Task Manager, started automatically at boot (very little and very few resource consuming). It make the green MCE button works
There is also another plugin, MPTray-Mod; it does the same thing, but (for me) causes problems in MP responsiveness.
2) How do I make it so MCE does not respond when I press buttons such as the "Live TV' button.
Uhm. In Mediaportal config you can map/remap remote buttons (and remove mapping, I think), give it a try.