Regarding the "shoot a number" theory, I think if you're in a tournament and trying to go nuts, then its ok to come to the course and say I need 70 to have a chance (or whatever). That will dictate how you want to attack, or not. Related, if you've got some match or bet that you're losing, and you're out of holes, then its ok to think that you have to birdie 18 or something.
But generally, I'm with you esepcially in normal play or non-terminal rounds of tournaments. Play the shot, go to the ball, play the next shot. There really isn't much global strategy there in a non-tournament round. I can't count the number of times I've finished 9 and looked at the card and said "Hey, I shot even (or 1 under or whatever) on that side." That's how golf is played.
For your practice tip, I used to do the "play the course on the range" thing religiously, but now, not so much. It helps to visualize shots, but now I think I get more out of hitting 5 or 6 of the same thing in a row to different targets so that I can recall confidence in that club. "I hit the 4 iron perfectly 10 times in a row yesterday, so taking it over the water on this par 5 shouldn't be a problem...) The one exception is wedges. Wedges tend to be more about distance control than other clubs, so those I will radically alter the distance I want, the clubs, etc., between shots. But, I think that's less about mental side of golf and more about skill and distance control.