How to jump on haystack on Inferno

So, considering the discussion in the comments, and my opinion, possible causes of the FPS drop and screen tearing for the specific game in question, CS:GO, would be (in order of likeliness)

• Corrupt configuration files on CS:GO. (OP already reset them, discarded)
• CSGO or Source Engine update issues (No updates were released at the time of the incidents)
• Busted drivers. (OP already reinstalled them so, discarded)
• Broken GPU fan, so it throttles down to prevent damage. (Op checked them, so discarded)
• Dirty GPU contats. (OP already cleaned the card, so discarded)
• Tweaking fps_max value. (Already done, discarded).
• Nvidia GeForce Experience causing issues. (OP uninstalled it, so discarded)
• Steam Overlay causing issues. (Op disabled it, so discarded)
• Windows update messing with OS. (Op stated that no updates occurred before the incidents)
• Nvidia HD Audio causing issues. (OP uninstalled it, so discarded)
• Busted Video Card (By OP's comment this turned out to be the culprit)
• Busted RAM (Unlikely)

At the time of this answer we don't have specific information about performance in other games, OP specified that the screen tearing was occurring on Borderlands: The Pre-sequel as well, but we don't have specific performance data. On the other hand Furmark stress tests didn't crash the card, but the issue in the games persist.

Given that information the only option we have left is a somehow damaged Video Card, the solution would be to fill a RMA, as the card was recently bought. I suggest contacting with the manufacturer instead of Amazon or Nvidia. The manufacturer (if professional enough) would give you a tested card, guaranteed to work, while Amazon will give you another boxed one or a refund if you are a regular client. Nvidia will do nothing they only build the chipset. I've had a reasonably good experience with EVGA for example, not sure about other manufacturers.

This answer is based on opinions from the community rather than facts provided by Valve.

The official answer would be: We don't know.

Kills do nothing when it comes to ranks.
The only thing that matters is whether you win or lose rounds.

Lose = you lose points (even with scoring an ace)
Win = you get points (even without killing anyone)

So if you're top scorer on your team and still don't manage to win more than you lose you'll have a hard time getting promoted. It's possible though.

How many points you get (or lose) depends on your current ranking (calculated in a system based on glicko2*), the sum of your teams points and sum of your opponents points, and whether or not you are MVP** in that round.

* Source
** MVP will be awarded to the best performing player from the winning team. Usually defined by good teamwork (Bomb handling, kills, assists,..).