Yes - you can use EPDM 2010 with SW 2009. The only thing you cannot do is take advantage of the new method of managing Toolbox files in the vault. That would require that SW be 2010 as well.
I have SWX2010 (SP2) running with my EPDM 2009 (SP0)
As far as i know answer is: NO
EPDM 2009 does't support SWX2010