Firstly, the program you are refering to is Crimson Editor, not Emerald Editor. Emerald Editor does not really exist. It is a program that was in a state of planning before Crimson Editor went open-source. Now it is somewhat stalled.
As for your first question, I think this post might have some useful info for you: http://forum.emeraldeditor.com/index.php?topic=572.0
. Basically, the associations and the syntax coloring settings are not connected. The process for setting up syntax colors is described in the first reply to the linked post. If you need more help specific to your problem feel free to ask.
As for increasing for size, that does not exist as a keyboard shortcut as far as I know. You can change the font size through Tools->Preferences->Fonts-> double-click default on the Screen fonts tab -> change the size -> OK -> OK.