First and foremost, don't give up yet! You are quite far away from your travel date, and prices are likely to change between now and then.
Second, set up some searches on yapta or airfarewatchdog for the flights, and they will let you know if the prices drop.
Third, I am able to see several options. Don't forget to click on Nearby (to the left of your search box), which gives you other airports. How about this itinerary:
Ticket one (Departure):
Washington (DCA) to Los Angeles (LAX) - Sat, Aug 3
Delta Washington (DCA) to Detroit (DTW) - Sat, Aug 3
Delta 2045 Dep: 5:15PM Arr: 6:55PM 1h 40m MD-90 Economy (U)
Layover in DTW 0h 45m
Delta Detroit (DTW) to Los Angeles (LAX) - Sat, Aug 3
Delta 1845 Dep: 7:40PM Arr: 9:44PM 5h 4m Boeing 767 Economy (U)
Los Angeles (LAX) to Honolulu (HNL) - Wed, Aug 7
Delta Delta 2365 Dep: 8:40AM Arr: 11:35AM 5h 55m Boeing 767 Economy (U)
Honolulu (HNL) to Kahului (OGG) - Wed, Aug 14
Island Air Island Air 104 Dep: 2:10PM Arr: 2:45PM 0h 35m De Havilland Dash-8 Economy (S)
Cost per passenger (including taxes & fees) $561.56
Provide this information to a
travel agent to help them match the fares found.
Make sure to provide the exact booking and fare codes shown.
Fare 1: Carrier DL UA21A0UY WAS to LAX (rules)
Passenger type ADT, one-way fare, booking code U
Covers DCA-DTW (Economy), DTW-LAX (Economy)
$188.83
Fare 2: Carrier DL UA00SONM LAX to HNL (rules)
Passenger type ADT, one-way fare, booking code U
Covers LAX-HNL (Economy)
$251.92
Fare 3: Carrier WP S HNL to OGG (rules)
Passenger type ADT, one-way fare, booking code S
Covers HNL-OGG (Economy)
$58.95
US Transportation Tax (US) $18.66
US September 11th Security Fee (AY) $10.00
US Passenger Facility Charge (XF) $9.00
US Flight Segment Tax (ZP) $15.60
US Alaska/Hawaii Departure Tax (US) $8.60
Subtotal per passenger $561.56
Ticket 2 (Return):
Kahului (OGG) to Washington (DCA) - Wed, Aug 14
Alaska Airlines Kahului (OGG) to Portland (PDX) - Wed, Aug 14
Alaska Airlines 822 Dep: 9:45PM Arr: 6:08AM 5h 23m Boeing 737 Economy (V)
Layover in PDX Thu, Aug 15 3h 22m
Alaska Airlines Portland (PDX) to Washington (DCA) - Thu, Aug 15
Alaska Airlines 764 Dep: 9:30AM Arr: 5:40PM 5h 10m Boeing 737 Economy (V)
Provide this information to a travel agent to help them match the fares found.
Make sure to provide the exact booking and fare codes shown.
Fare 1: Carrier AS VHASZN4 OGG to WAS (rules)
Passenger type ADT, one-way fare, booking code V
Covers OGG-PDX (Economy), PDX-DCA (Economy)
$387.25
US Transportation Tax (US) $14.75
US September 11th Security Fee (AY) $5.00
US Passenger Facility Charge (XF) $9.00
US Flight Segment Tax (ZP) $7.80
US Alaska/Hawaii Departure Tax (US) $8.60
Subtotal per passenger $432.40
All in, $994 per person, and you ride on Delta on the way out and Alaska on the way in (via our great city of Portland

).
Also, there were several options at these price points, including with Island Air.
As for interlining bags, both US Airways and Delta has said they will not interline on seprately tickets trips (like you were suggesting), plus they don't interline with Virgin America (VX) nor JetBlue (B6).