Any idea on what keyboard shortcuts to use to access tablesorter controls in column header? or software handlers/other to support 508 compliance (to support accessing these controls via the keyboard)?
For this, I would definitely go with a pre-existing library. There are some nuances to accessible tables that can eat up time, and can be hard to test for if you don't have experience with a screen reader.
My favorite, when it comes pretty tables, is YUI 3:
http://yuilibrary.com/yui/docs/datatable/
Their library is solid, and their documentation is fantastic. Just make sure to follow their examples to get the full benefits. You can take an accessible library and make an inaccessible site quite easily.