Scanning no, but to intercept keystrokes would require root access.
Common misconception. Local access present creative opportunities for phishing from code injection to creating facades to existing apps.
The Palestinians are paying for the trip and they get to set the conditions they pay for; that's the way all invited talks work. "No side trips" is a common condition for invited talks.
Nonsense. Are they requiring him to get on a plane and land in US? I don't know what kind of deal RMS got for himself but I am pretty sure it is quite uncommon that organizers require you to go back to country of origin after the engagement is over. He should have negotiated fee for giving talks like 1k/hour and pay for his trip himself and not be restricted in his movements.
People who go to conferences are the ones who shouldn't.