1)
Why was Moshe afraid that he people would stone, seeing as they were only placing the legitimate request of asking for water?
1.
Oznayim la'Torah: Because what they were apparently asking was for a permanent solution to solve their thirst in the desert, 1 just as Hashem had arranged a permanent solution with regard to their hunger, something which Moshe thought was impossible to attain 2 and therefore perceived as a threat to himself.
2.
The fact that they came to quarrel with Moshe turned it into a personal issue, 3 and Moshe felt threatened.