Objects carried on the sUAS are secure.   The site supervisor has approved the flight. ATC has granted clearance.

ensure that the human beings who are not participating in the operation are under a covered structure or inside a non-moving vehicle. ensure the sUAS is equipped with a parachute make sure the area is closed or restricted-access.

No, 14 CFR Part 107 only applies to sUAS weighing less than 0.55 lbs. Yes, there is no lower weight limit for operating under 14 CFR Part 107.   No, roof ...

Use a “buddy box” system with two controllers. Use a radio system to instruct the non-rated pilot. The Remote PIC cannot supervise a non-rated pilot.

No more than three as long as the Remote PIC maintains visual line of sight. As many as he/she can handle. No more than one. 

Person manipulating the controls. Visual observer. Remote Pilot in Command (Remote PIC).

visual observer. remote pilot-in-command.  owner of the small UAS.