Physical access should not mean getting close with a wire, it should mean opening the case and messing with the internals.
Your personal preferences are irrelevant to a concept that has been proven over centuries. Physical access is physical access, and I can get root while sitting at most unix-like OSes (including yours) without touching a nutdriver.
1) As much time as you need, within reason. 2) Privacy complete the attack.
Physical access should not mean getting close with a wire, it should mean opening the case and messing with the internals.