Pretty much... I was even thinking to have the boundary event attached directly to the call activity, but after quick check it seems it is not supported at the moment.
Regarding the termination of the process on error end event, it should be ended but only the sub process and the main process should still run but seems like it does not work like this. Moreover error end event should throw an error event so other parts of the process could handle it, and I think it's not supported either :(
So, as an alternative you could use signal events instead of error events in quite the same approach.