When to push e5

This early e5 push only served to open up the light-squared diagonal Black's King sits on. 

Questions:

1) Is white's e5 pawn push only worth it if it can be accompanied with enough pressure to delay black's knight from returning to f6 long enough to launch my pawn to h5?

2) Is the open diagonal to black's King generably reasonable compensation for trading off a central pawn and the 2 tempo spent doing so?

What's with Bf4? That move has no part in a KIA set-up. 3. g3 looks more accurate (or even better, 2. g3). If that Bishop had still been on c1 (where it belongs) you would not have lost a tempo to Nh5.

Yes, totally agree with blueemu. For this to be a KIA you need the kingside fianchetto and 0-0. And the KIA DSB remains on c1 until such time as it's destiny becomes obvious, and then it often plays a decisive role.

As others have said, playing Bf4 that early is not best as the Bishop can be vulnerable to Nh5 or even g7-g5. The Bishop can developed to f4 later after the e5 pawn push.

To answer your questions, the drawback of Black playing f6 is that it creates weaknesses in their position, namely the e6 pawn and the e5 square. Here is an example:

So when your opponent plays f6 you usually take and then shift your attention to the newly created weaknesses on the e-file.

We usually only push e5 after the opponent has castled, that way the center will be closed and you will have a strong attack in the king side.

think about e5 pawn as a poisoned one, if this pawn managed to reach the 6th row and that's like fisher did in his 1970 game.

I was trying to analysis the same thing so baiscly e5 helps to make opponent uncofortable, which mena he will play he is not favored to play.

in the game you presented, I think pushing e5 pawn was mistake, fisher played same line, 
he took the bishop back , and made D knight more active. 
when am thinking about the game you put I think the mistakes was :

1 - not casteling , attacking king side and not casteling lead to not active pieces: like white Bishop and King Rock.

Me vs Roland Basque (1900 OTB rating), at classical time control (40-in-120).