Yes it will be two separate tickets as the IAD departure will be on BA using miles and DL doesn't partner with them and I'll be paying for that ticket.

p.s. added 2:10p cdt . . . called DL and they said I could check my bags all the way through from DL to BA so that is great news! I will probably get my bags at IAD coming back, however . . . since I'm thing about overnighting in NoVA to visit my sister on my return.

Thanks again!