I think that the HNL-IAD NS is gone, at least for the season. The reroute is simply an auto-placeholder so that you've got something.

The separate PNRs is only a problem if the second is OA. If both on UA, don't worry, just look at other combinations which get you between HNL and your final destination and then call UA.

If the second PNR is OA, fee-free changes to the second PNR will be messy.

If you posted your actual itinerary, FT could be more helpful.