First Time Playing Sicilian. Mixed Feelings.

1. After I forced the capture of the knight, my opponent was down material and seemed to playing a materialistic game, avoiding my wonderfully-placed bishops staring down on his bishop on the a8 - h1 and the b8 - h2 diagonal. When he finally saw the threat, he still failed to respond with accuracy, opting instead to fight for material. More often than not, I get caught up in playing for material. How would you recommend I eliminate unnecessary materialism when I am on the receiving end of a royal punishment. Of course, a queen and rook down demands a courteous resignation, but being 2 pawns down? When should a game ever become about regaining material before going for mate once more, from a more experienced point of view? (My surname isn't Tal so no, I can't win a game 9 pawns and 3 kings down) 
2. What was the best way to take advantage of his queenside weaknesses after the blunder with the knight (ultimately resulting in its loss) 6. Nb5? My attempts weren't at all effective, and I feel that I could really have gave him some more trouble on the queenside (possibly even traded queens to enter a favourable endgame) before shifting the attack over to the king.
3. I've been doing some endgame study. (Basically memorising the theory of different endgames and utilising knights and bishops more effectively). Hypothetically, if one were to assume I hadn't spotted the mate and we just went on to trade into equality with just rooks and pawns left on the board, what would the endgame situation look like? Assuming black immediately began playing at a brute force theoretical level, what situation would the endgame collapse to, and has my play been wise with regard to the possibility of queening a pawn equating to a win? (I am interested in how forceful middle-game attacks influence the structure of the endgame)

I genuinely would appreciate the feedback  Really looking to improve my chess this holiday (currently a 12th grade student) with the hope of getting into the Uni chess team. Also, on a somewhat unrelated topic, where should I put in most of my efforts to get to a comfortable rating for university chess team. I'm from SA, so it isn't AS big of a deal as it is in Russia or the US, but it's still tough. I pretty much would love to be able to reach a rating of around 1700 (partially but not overly ambitious) with 3 months devoted almost entirely to the study of chess.

 

P.S I read more about chess than I actually play like chess so my verbose writing can be accredited to my GN status #grandNoob. 

 

Tl;dr: When is materialistic play a necessity? How should I have better capitalised after 6. Nb5 Qa5+? How do we play a solid middle-game while still creating a favourable endgame if we were to just simplify by trading away everything except our pawns and perhaps rooks? What are the best ways to improve overall chess rating from 1200 - 1700 (my attempt to quantify the improvement, though my rating is less important than my actual abilities) in a few months of devoted study?

You shouldn't be concerned with the specifics of one game like this one. I know you would like to know a more efficient way of taking out your opponent after he blundered the knight but specific advice will not help you become a better chess player as you will play many games and cannot possibly memorize them all. What you should be concerned with is understanding common ideas to employ when you are winning. There are a lot of good books on the subject. I don't know of any off hand, but I'm sure Dan Heisman written a book on the subject. Google his name and see what you get.

The only games you should be memorizing is master games. Not that I think you should memorize tons of master games, as that would go against what Dan Heisman teaches, who is a really good chess coach, but, if you ever want to memorize a game, let it be a game a master played, not one like this.

Understanding general principles is more important than understanding how you could have done better in an already won game. it's best to study games that you lost, with a stronger player...

don´t be a sheep,  if everybody plays sicilian you should try another opening , d0n´t become in a herd animal

The Sicilian is pretty sharp and there's tons of theory to know if you want to play it regularly. Honestly, at your level, I'd advise the Caro Kann. Might come back to this later, as I just woke up and I haven't had my coffee yet lol

Just play the closed sicilian dud.