Yes, another HND-NRT question about very specific conditions. Sorry for the small dissertation.

At the end of a complex itinerary, we're Flying PEK-HND/NRT-ORD.

Booked via UA, but these legs are on NH.
Flights are on a Saturday, and we're booked in P/Z
Two of us on separate tickets (one single ticket each), same itin.
There's no way we can avoid checked bags as this is the end of a long trip.
I booked this since it was the cheapest option by several thousand dollars.

Most connecting information I've seen assumes arrival at HND T1/2, but the PEK flight will arrive at the INTL terminal as far as I can tell.

The details are:

NH 979 from PEK arriving HND at 12:50. This arrival time seems to be mainly theoretical, as it is on time only 24% of the time and "excessively late" 29%.

The next flight also NH, is NRT-ORD with a 17:10 departure, which in theory gives 4:20 for the transfer.

There is a huge hole in the limousine bus schedule at this time - there is a departure out of INTL at 13:10 and then nothing until 14:40. The 13:10 seems impossible, the 14:40 doable unless the flight is very late.

The 14:40 would give us 1:50 to absorb the almost certain delay and clear immigration, buy the tickets, and make our way to the bus. We'd then have 2.5 hours from the time we set foot on the bus until the ORD flight departs, which seems OK.

I assume we'll be checked through at PEK, and we'll be in business class. I assume/hope the bags will be already checked so we just need to drop them at NRT and go through priority security?

There are 4 other buses that leave T2 between 13:10 and 14:40, so I'm thinking if we clear baggage and immigration quickly we'd be better off taking the shuttle to T2 and then catching the bus from there? Will the ticket office in the INTL terminal sell a ticket for a T2 departure? I'm thinking might be preferable since they would also advise on the best option for us.

Or, would it just be better to dump the bus completely and take the train to Shinagawa and catch the NEX from there.

The last backup is that there are several later flights (with connections) out of HND later that night, so I guess if NH really messes us up we could get rebooked. If things go south early I'd start that process before we even leave PEK, and maybe they'll book us over to the PEK-ORD direct flight.