Not as much as you do, I’m sure. I’ll admit that most of my knowledge is derived from Anthony Beevor’s book, plus second-hand information from studies of artists affected by the conflict (esp. Picasso and Robert Capa), not from primary sources.
However, I didn’t mean to suggest that assassinating Franco would have prevented the Civil War (it would have happened without him, as you point out), but that his absence would have deprived the Nationalists of a very strong commander. This would possibly have given the Loyalists a slightly better chance of victory. I’m not sure if Sanjurjo would have been able to unite the various Nationalist factions (Carlists, Falangists, etc.) under him as effectively as Franco did.
And if the Loyalists would still have lost against Sanjurjo or Mola or whoever else would have commanded the Nationalist armies in Franco’s absence (as one could certainly argue would have happened anyway), then maybe the repression and executions that followed the civil war wouldn’t have been as severe as they were under Franco.
That’s probably a very naive hope, however.