Update: I have since gone back to letting SQL Server and Crashplan run in the background as normal. It's just not a battle I can win. Yes, if I do what I described in the previous post, I can cut the idle utilzation down when nothing is open, but in any real-world scenario (Visual Studio is open, a browser is open, etc.) there is high idle usage anyway, so if I really want to save battery power I might as well just shut down the VM.
My colleague is running a very similar environment but he is hosting it on Windows using VMWare Workstation. His idle CPU with SQL Server, several instances of Visual Studio, browsers, etc. open is 1-4%. There is definitely something not right about VMWare Fusion in comparison.