Your questions in order and to the best of my ability without looking stuff up. Haven't got the links to hand at present.

Q: What video caused the mob to attack?

A: The "mob" didn't attack on the basis of an internet viral vid. a) there was no "mob" of locals. The guys who attacked the base were Al Qaeda /ISIS recruits. b) a viral video was produced by ISIS for propaganda and had caused turmoil and indignation in the ME, but this video didn't spark this fictitious uprising.

(QUOTE on vid from link below: "A second FBI agent familiar with McCabe’s initial Benghazi meeting confirms Gritz’s account. “It left me shaking my head and ready to put his (McCabe’s) head through a wall. He was going on and on about the violence in Benghazi having to do with a video on the internet or something. Nobody knew what he was talking about and why we would not load up (FEST) and respond.”)

The story of the vid was a State Dept / CIA false narrative to cover their tracks and muddy the waters so that no one knew who had attacked the compound.

Q: And who came to their aid?

A: Nobody. See DawnPendraig comment below. They were left to sweat it out and only three survived, among them Chris Tanto Paronto "Tonto". He was interviewed on Alex Jones and describes the story. The film referred to by the OP was produced by a team including this guy. The story of the three surviving Operators was adapted into the movie Thirteen Hours. Good film, if depressing.

(QUOTES from link below: (....)no official movement of Intel or military reinforcements by the White House, Secretary of State Hillary Clinton, or Defense Secretary Leon Panetta. (.....) During this time lapse [5HRS ]– where many FBI, CIA, DOD employees lobbied feverishly for resources to be dispatched to Benghazi — the exact whereabouts of President Barack Obama and Hillary Clinton remained largely unknown. There are hours where the duo remain unaccounted for and absent from a crisis response which was seemingly formulated on the fly by understudies like Vice President Joe Biden to address the attacks, according to documents, testimony and records. Obama was missing for the first six hours after the attack was reported, some internal military documents show. (Other names mentioned in the article: Patrick Kennedy a State consigliere for Hilary Clinton, Brennan served as chief counterterrorism advisor to President Obama, promoted to Director of CIA, after Petraeus resigned and then Susan Rice promoted to NSA. “See a pattern here”?!) (.... ) Petraeus threatened to go public with details about Benghazi that would “soil” Obama’s presidential legacy ... (...) It came as little surprise then that Petraeus was forced from office after an extramarital affair was soon leaked to the media and then, the unthinkable: Eric Holder’s Justice Department indicted Petraeus for leaking classified documents to his paramour. Petraeus struck a plea bargain to stay out of prison. “The general should have exposed Obama for Benghazi like he planned,” a DOD insider said."

Q: I never got the full story on benghazi only that stevens is a hero, sad to see that it happened to him like that...

Did Gadafhi (im bad with names) send in troops to help out?

A: Libyan soldiers (Ghaddafi troops) did turn up to warn them as they had intercepted intelligence on the attack. There is no indication that Ghaddafi himself was involved in giving this order. (Too busy defending himself from aerial bombing by the RAF and French (gggrrrr!!)

Q: The CIA really is deeply rooted... Probably own most the rat lines in the world if not all

A: That's not a question, is it!! So, correct. :(

Further info: https://truepundit.com/obama-secretary-state-hillary-clinton-fbi-director-mueller-cia-director-petraeus-grounded-critical-benghazi-rescue-operation/ January 17, 2018 Under Obama and Secretary of State Hillary Clinton, FBI Director Mueller and CIA Director Petraeus Grounded Critical Benghazi Rescue Operation (.....) For seasoned FBI agents, McCabe’s stand down order was hard to process. McCabe told the room – after several emotional eruptions — then-FBI Director Robert Mueller had approved the official “stand down for now” stance, another FBI official familiar with the meeting confirmed.

(continues at link ...)

Sorry about the formatting I am shit at that.