Colludium
Strange...my current project is up to ~850 events, but I haven't had any stability issues. In fact, I don't think I can ever remember C2 crashing or hanging on me (unlike CC). Did this just start with r190?
The only difference I can think of is I'm on Win 7. Also, I tend to stop/start a lot, so I'll make a handful of changes, test, save, close the editor, and bring it back up. I don't tend to use 'undo' a lot either, unless I have to.
SecondDimension
I don't have steam, so I can't give specific feedback there. It does seem like, out of the few people who've had issues with the C2 editor, many have been using the steam edition. I think some of the blame comes down on steam itself; their services are great, but I've never been fond of their software.