Awesome. Thanks for this.
1b is fixed.
Working on 1a and 2.
4 is expected behavior. When Universe Sandbox is no longer the focused window it does lower its CPU priority from normal (what most programs are) to below normal. So while it will eat as many CPU cycles as it can get, it shouldn't get in the way of other programs.
It would appear you have a dual core machine (55% CPU usage). Once we move to .NET 4 and add good multi-core support this should be much higher than 50%.
When he said 1a, 1b, 2, and 4, he meant 3 for 4.