Schedules are subject to change, but as of right now, the HPN-ORD would connect to the last flight of the night ORD-LAX. There are no other connecting options ORD-XXX-LAX that night either.

The 5:40 DCA-LAX that OP would connect to is the last non-stop of the day (there are only 2 DCA-LAX non-stops per day since they must use perimeter exceptions). The only other option to LAX remaining after that is a 6:25pm DCA-ORD connecting to the above ORD-LAX flight. So if the OP is slightly delayed and missed DCA-LAX, there's a chance, but not much window for error there either.

Again, schedules could change as this is still a bit far out.

I'd consider going down to JFK and getting a non-stop.