Bainer,
IMO, as soon as you knew what was going on with the jerk manager you properly ejected you should have:
1. halted the game.
2. announced that it would not continue until the ejected manager had left the premises.
3. if he had not left the premises within whatever you considered a reasonable amount of time, announced that the game was suspended and leave it to the league to decide how they want to deal with it.
I actually believe that your second ejection was improper. The second ejection was a result of your failure to enforce the first ejection.
I also believe that you do not have the authority to declare a forfeit in the situation you described, as some have suggested. I applaud your response in saying you would not abuse your legitimate authority in issuing additional ejections to the point that you would have the authority to declare a forfeit.
Now, if the ejected manager refuses to leave and you do suspend the game, if I'm on the league BOD, I might be inclined to declare the game a forfeit. I would certainly be inclined to suspend the offending manager for (at least) the remainder of the season.
But hey, I'm just a coach (and a BOD member), so I could be wrong.
JM