I think the reason Hurley would have dived after Dave is that Dave was messing so much with Hurley's head. Hurley was rather unbalanced at that time.
I think Sawyer sees Hurley as a friend. Remember when Hurley asked Sawyer for the manifest and Sawyer let him have it without much ado. Especially when Hurley reminded Sawyer he needed the points!
I think Hurley took a lot of Sawyer's rude nicknames in his stride but then Sawyer caught him on an off day and Hurley broke. However Hurley seems to forget that nicknames are often a sign of affection as well as derision!
Hurley is a fairly easy going chap and I don't think he would see many people as his enemies and would perhaps see everyone on the island as a friend.
I would think Hurley thought Sawyer's sacrifice was enough - no need for anyone else to jump out of the helicopter. It could have made Sawyer's jump meaningless if everyone jumped out!!!
I still think Sawyer was brave to make that high dive in shark infested waters! I wouldn't do it!
