About #3, lots of comments already on skydivers forums.
Looks like the Beech 18 looks really cool but isn't best suited for skydiving: relatively low powered, low tail (risk of a jumper hitting the tail), elevator in the burble when skydivers are hanging at the door, CG out-of-limits if too much skydivers at the door during jumprun.
Apparently, jumpers wanted to make a big way (group) exit (12 jumpers) and discussed with the pilot who said it was ok but he would have to fly the jumprun faster to avoid stalling (old time jumpers are saying that they never jumped groups bigger than 9 back in the day when Beech 18 was regularly used as jump plane, and in those case the remaining jumpers were cramming themselves as far forward as possible to keep the CG manageable).
Pilot took off downwind (12-14mph wind) with full fuel load and full jumper load, barely clearing the trees. This did not contribute to the accident but maybe points to some lack of judgement on the pilot's part.
Did the pilot forget about the pre-takeoff briefing? Anyway, he slowed down a lot for the jumprun with the flaps up. Stall while jumpers were positioning themselves at the dorr, violent wing drop, plane got inverted and dove straight to the ground. All jumpers managed to escape, last one above 6,000 ft. Videos from the Go-Pros that some jumpers were wearing are said to be chilling, though (probably seized as evidence).
Pilot wasn't able to recover obviously and couldn't bail out. Blue Skies to him and condolences to the family.