To more directly answer your question…

The large majority of trips on the 787 and 777 in EWR are commutable on both ends (787 a bit more than 777 because it does less domestic). The trips are generally pretty efficient so most lines are 18-20 days off. The 787 in EWR is WAY overstaffed right now so I doubt it’ll be available in the next few months until deliveries pick up. Network Scheduling shifts the flying back and forth between the 767/777/787 faster than they can move the pilots so you can get some weird imbalances sometimes on those fleets.