According to my sources foreign backed media were broadcasting phoney exit polls to discredit the official result.
The difference between the official result and the exit polls is that the official polling is verified by officials from each party, exit polling is entirely informal and verified by a random journalist. It's very common that people vote one way in private, then publicly claim they voted the other due to social pressure, thus any journalist can pressure people into lying about who they just voted for.

The violence is mostly communist linked university groups throwing stones, police response is mostly teargas, I'm hearing less then 5k protestors. That's a lot, enough to damage public buildings, and thus the army was called in to essentially protect riot police. Several protesters were killed from what I've seen, but I've also seen footage of protests armed with Molotov.

There have been persistent attempts to tip the state because it's position to the US and specifically to US oil companies is less than friendly. US special forces were kidnapped in Venezuela several years ago after being caught heavily armed and red handed attempting to organise a coup. So keep in mind the democracy is under both external and internal threat.