after 5...g3 he looses control of the dark squares.  Now he has to use peices to defend the a1-h7 and the a3-f8 diagonal (he only has one bishop so this can prove to be difficult).  Actually according to Fritz, he has 4 viable continuations the most played is 5...Qc7.  Also is 5...a6 produces a mild threat of b7-b5, but I have never been hurt by b7-b5.  He can also play 5...Nf6 or 5...d6, these seem more solid to me.  I usually dont play the sicilian for black I only play it for white.  I need to start.

The analysis is right though.  You should have played 7.Be3.  He would be foolish to take your knight because after 7...Nxd4 8.Bxd4 Qxd4 his dark squares become major weakness. Not only that but your attacking his rook so he has to defend by further weakening his position.  Also, after he looses his bishop on g7 the king no longer has a safe place to castle.

After 8...bxc6 blacks position looks horrible.  He has nothing guarding the a5, c5, and d6 squares.  These are scrumptious outposts for your knights.  You should be trying to come up with a plan of placing your knights on these squares where they will wreak havoc on his terrible fortress.

9.Bd2 is way, way too passive.  Now his dark squares are fine.  He has no worries anymore because you blocked your wonderfully active queen (she was beautiful) and your key peice for exploiting his weaknesses is stuck defending a knight he wouldnt want to take.  You would hope that he would trade his bishop for your knight.  If he traded, he could only hope for a draw, because he would be dead lost.  Better would have been 9.Bd3 attacking your wonderful outpost on c5 for your knight whose just itching to get there via Nc3-a5-c5.  Or you can iritate the hell out of him by 9.Bf4 where he shoots a horrible lazer beam through his position down the b8-h2 diagonal.  At this point black would be crippled.  His safe squares are running out in his own camp.

10...d5 was actually very good.  After cxd4 he now has a large control over the cenral light squares.  If he castles then his position would be ok.  All he has to do is a6-a5 and Ba6 and he is in a winning position:  Good pawn structure, two very active bishops, safe king, and alot of space on the queen side, with good attacking lines.  White handed the position over with Bd2.  Amazing how playing a passive move allows your opponent to turn a terrible position into favorable one.

12.f4 was ugly as you said.  At this point its no longer an opening becuase you have left opening lines along time ago.  You should be thinking about the stratagies of the position and forming a plan of attack.  It also blocks your bishop and prevents it from going to its most active square (e3 isnt a bad square for your bishop either).  Also, you open up the dark squares around your king.  At this point blacks dark squares are exceptionaly open for his queen and bishop where they can mover around the board swiftly. 

14.g3 just opens your king up more.  With his active bishop and queen and bishop with alot of space, you nearly committed suicide.  After this point your position just gets worse and worse.  But, great comeback though on the 20th move, if was only for a short while. 

Good game.  A perfect lesson on why one should play as actively as he can and exploit your oponents weaknesses.  As a general rule, if your oppenent has weaknesses its best to act on them as fast as you can, before he corrects thoseweaknesses.  If you have alot of weaknesses yourself you should stay back as he did and correct them.