4 - I don't know about boeings, but any failure mode in an airbus that knocks out both autopilots, also puts you in alternate or direct law, which is a very different flying "feel" to normal law, and certainly something you couldn't and wouldn't want to practice on the line if you valued your job
The aircraft might "feel" and behave differently in alternate law/direct law, however the instrument scan is exactly the scan.
A good instrument scan is very important when hand flying no matter what control law.
A good scan developed and practiced in normal law will help you fly better when in alternate law/direct law.