I created a ticket for bug #1 you reported. Going to point the web UI team at this thread tomorrow to handle the rest.
Not entirely sure form validation on loading is expected. Required fields are indicated by a * in the UI that may need more distinction, and if you provide no value for an empty but required field on form submission it shouldn’t be surprising that validation fails. I don’t think the behavior in 8.1 would have been different, but I’ll leave this up to the appropriate team to decide.
Known issue, see 3rd Party Modules, Vendor Name .
Module hot loading was removed for 8.3 and won’t be coming back.