I'm actually surprised to hear this isn't working. I use a custom sort implementation when "Custom" is used as the sorting method on the Songs tab that is supposed to sort numbers correctly, but use alphabetic sorting when identical numbers are encountered. I just tested this myself and it works correctly. I assigned the numbers 1, 2, 10, 11, and 20 to five different songs in the library. I then tapped "Sort" at the top of the songs tab and selected "Custom". The songs were listed in the expected order - 1, 2, 10, 11, and 20. If this isn't working for you, I'm going to need additional information as to how you are setting up your songs, and what sorting options you may have changed.
You can't currently rename Custom or Custom2. I may support this in the future when time allows, but it's not a high priority at the moment.
You can't currently rename Custom or Custom2. I may support this in the future when time allows, but it's not a high priority at the moment.