Arena Pushing (Key of Memory Breakpoints) Discussion/Strat

If there is a discussion on Arena or guide somewhere feel free to post. I wanted to discuss “How” to push Arena effectively and use Key of Memory for short playing periods. Example

I want to play an hour before bed after work when can I portal to town to “SAVE” my place with an Arena Key of Memory. If I portal at 290 because I’m tired and want to sleep or need to stop will the Arena key of memory pick me back up around 290?

What are these breakpoints so pushing is possible and strat too push. Just don’t really want to waste time and portal at wrong point when I needed 10 more waves to have a higher “Save” point.

From what I understand Key of memory sets you back some amount of waves but hopefully it’s not too far so you just are wasting time to get back to where you were. Ideally I’d like to do a 100 waves or so and log out then pick back up again latter because I had things to do or the next day.

Question on Leader Board - Is 1 player meaning 1 player partied with you? So Solo is the true individual leaderboard?