DCA-BUF-ORD-SEA / YVR-LAX / OAK-HNL best fare
You're probably better off pricing each segment separately. Hawaiian often has sales on OAK-HNL. You should also look at SFO and SJC. Southwest flies BUF - Chicago Midway, and Midway to SEA. there's not really a need to have all of these on one ticket.
The only way to get free bags would be to get credit cards for the relevant airlines, or fly Southwest.