The group "feed" and the "discussion" are basically two different things. The main "news feed" in a group is basically like "FishHook"... newest stuff at the top and the rest just scrolls off the bottom. The Discussion is essentially a forum section in the group, you have threads/replies/etc. like in any other forum section.
I'm not gonna dictate how a group uses each one, that would defeat the purpose of giving you guys some control over it. If you're just wanting a group to banter back and forth then probably the feed is all you need. If you want to actually be able to easily refer back to topics, etc. like the regular forum, then use the discussion.
IIRC activity (but not the "news feed!") shows up in the "new posts" section (NOT the general home page). You can see all of your groups feed activity by going to the main menu->Groups->"your feeds". which has then separate tabs for feed/threads/events.
It all *looks* confusing but its really not, I don't think. Just more options that you can use, but don't have to if you don't want.
My main intention with the whole groups addon was to give you guys a way to (wait for it) form groups (I know right) like your local car clubs, specific interests, regional stuff, like that where maybe a little better sense of community might exist, versus trying to track a single thread (or many) in the sea of the greater forum at large... at one point I tried to give some car clubs their own forums, but it was clunky and required me to be really hands on with setting them up, setting moderators, figuring out permissions, etc.
As long as you all follow the rules (politics/harassment/etc.) about what the groups are, I don't really have a problem with setting up groups that might be considered off-topic even. Just remember all the rules still apply for content inside them.
So "green bay packer fans" talking about the Pack in that group exclusively (not cluttering up the main forum like you say, and keeping it easy to find) or "Rocket powered bassett hound enthusiasts" or whatever would be cool.
But yeah what you did with the events is cool. Make a group event, cool, post a thread in the main forum Events section, cool. Link them, also cool. Not going to get real picky on that kind of thing unless it starts to be a problem, which I'm not sure how...