Tidefan,
Sounds like your league president understands his and your respective roles in cleaning up the league. That's good.
As to your second question, I'm probably one of the least qualified people who posts here to answer it. I've never umpired a real baseball game in my life, so I've never ejected anyone. In twelve years of coaching, I've never been ejected.
If you are a subscriber to the paid part of this website, I would encourage you to read the following articles written by some of the distinguished umpires who publish there that address the question you raise:
Carl Childress
Why and How to Avoid Ejections (3 Part Series)
How to Talk to a Coach
Tim Christensen
Rats, cheese, and a glass of whine
The art of ejection
Rich Fronheiser
Game Management (2 Part Series)
Bob Jenkins
Traffic Stops, Misdemeanors, and Felonies (focus on Fed, but generally applicable)
Peter Osborne
Creative Ejections (11 Part Series)
I'm sure there are others as well.
If you do not subscribe to the paid part of the site, just use the forum "search" function with 'ejection' as the search argument.
In general, I believe that the best umpires tend to have the fewest ejections. This is because they:
1. Tend to make the correct call and are in position to do so.
2. Have excellent game management skills that tend to defuse "situations" that could lead to an ejection if handled poorly.
3. Have absolutely NO hesitation in ejecting someone when his behavior is deserving of an ejection (their reputation precedes them).
In the case of this league, one or two early-season ejections of the primary miscreants might be appropriate just to "set the tone" for the remainder of the season. If you and the league president believe that is the case, you simply MUST read Peter Osborne's series on how to go about doing it.
JM