With regards to replying to emails, are my expectations too high from Group leaders?
As I have come to do again and again lately, I completely agree with @Buffy. You need to calm down and take it easy. 

You have no idea what might be the reason for them delaying a response, it could due to:


delays with the paperwork to the rest of the faculty, 
delays with interview all candidates, 
delays due to other urgent matters such as grant/paper deadlines, 
or simply some sort of personal emergency


2 weeks is not an insultingly long time, so you have no basis on which you can demand an answer. These are busy people we are talking about. 

On a different note, it wouldn't prevent me from applying to somewhere else. Everyone who has ever applied to a position, or hired a person, knows the dynamics of this "game". Apply to other places if the wait stresses you, and you can always say that you had a more favorable position when you turn down a position. As long as you haven't played foul (i.e. lying, withholding important information etc) nobody should get upset.