BOS - Term B to Term E in 35 minutes?
 

Due to schedule changes, my international connection is now 53 minutes, and the inbound flight has been an average of 22 minutes late over the past two months. This is sounding too tight to me. Is 30 minutes enough time to do the bus from B to E, and even if I make it, will my bags? I'd just like some confirmation as to whether or not I should request a routing change from the airline, and some ammunition if I do. (Inbound flight on American arrives at 12:57am, outbound flight on Cathay departs at 1:50am)

First, I wouldn't take the bus unless you are either heavily laden or have difficulty walking. I'd walk through the central parking garage. Faster unless you walk out of B just as a bus arrives, but what are the chances of that - especially at 1 am? There are plenty of signs.

That said, I personally wouldn't try it. There's no airside B-E connection, so you'll have to go through security again in Terminal E. Even if you arrive on time it will be very tight, perhaps not doable, With any delay - and at that hour, with minimal airport staffing, there can be delays with the gate and jetway even if you land on time - it's way to close for my taste.

The only "ammunition" you need with the airline is the objective fact that the domestic-to-international minimum connecting time (MCT) at Logan is 60 minutes. They have given you a connection that violates MCT rules. Whichever airline ticketed you cannot, and will not, object if you want to change.

Change your inbound flight. 53 minutes might not be enough, and 35 minutes certainly isn't. Also, the MCT for AA to CX is explicitly published as 1 hour, 30 minutes at Logan, so you should have no problem getting the ticketing airline to change your flights.

This is an "illegal" connection as it is below MCT. It should never have been sold as a single ticket. At some point, even at check-in, you will be forced to rebook. By that time, there may not be space or only lousy space.

Before calling anyone, do the research as to what is available so that you can choose the earlier flight or an alternate connection point. Do not rely on a phone agent to provide useful or accurate information.

Once you know what is necessary, call the ticketing carrier (or TA) and remind them that you hold a below-MCT ticket and that it needs to be changed. Then provide the flight numbers.

This is also not a physically doable transfer. In 35 minutes you cannot deplane, walk out of and into another terminal, proceed through another checkpoint, and to your gate before the gate deadline.