I dont think speed chess can make you better. Thats comes from study. I believe Blitz chess should be played for fun, and I think most people approach it that way. There are many contradictions in chess, one i always found amusing was how GM Walter Browne is one of the best Blitz players around, but always managed to get in time trouble at normal tournament time controls. Yes, fast chess can make one play rather superficially, but I'm not sure that it makes you play that way in regular standard games. One thing Blitz has going for it is you can get a lot of "experience" with a new opening, trying a succession of variations in a small amount of time. Just don't put too much emphasis on the result of the game when evaluating the new opening.

Chess is a game of accumulating small advantages, then converting these small plusses for larger ones along the way. Of course when the opportunity for winning material or checkmating comes up, then take it, but going for mate from the first move is usually doomed to failure.

Well you may have answered your own question: the King's Indian IS good, so I suspect that you are losing for another reason. The Sicilian is more of a semi-open game, while closed positions crop up more in the King's Indian. Maybe this is your problem and you need more experience in closed positions. Remember that in closed positions, development is not always as crucial. Where your pieces ARE is not as important as where they can go TO, and how quickly. Breakthroughs via pawn levers are critical. In the King's Indian, black almost always trys for the break .....f5. This is virtually the only way to guarantee counterplay against white, who enjoys a bit more space in this opening. Nomzovich's "Blockade" and "Chess Praxis" are great books with lots of ideas concerning closed positions.