I think your valuing of moves is flawed. Yes, during the fuseki the best move may be worth 20 points. But there are often many moves that may be worth 19 or 18 points. So, playing perfectly only gains a few points compared to playing acceptable moves. In comparison, tactical situations often have a crucial move that wins many points - in low-level play swings of over a hundred points are not uncommon. There, missing the crucial move can lose the entire game, no matter how perfect the opening was played.
And does this set of tutorials give any idea of "best" or even "acceptable" moves?
There's no discussion of 2-point jump, 1-point jump, horse-move, diagonal move, loose play or connected/strong play in this set of tutorials. Or the value of 4th row (center-oriented influence play) vs 3rd row (edge-oriented territorial play). I'm not seeing any discussion on invasions or defense of invasions.
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I'm like 9kyu. I'm no expert. But I'm certainly at the level where tactical geniuses beat me in many positions, but I just wreck a lot of n00bs in the opening, and hold out until the ending.
The good news about opening theory or middle-game theory is that if the opponent is playing tenuki (ie: they ignore your most recent move and play somewhere else on the board), you're probably focused on the incorrect area.
On the other hand, if you're up vs a weaker player, YOU need to be the one playing tenuki. Its surprising how awful players are at double-digit kyu is at this. You will only see tenuki opportunities if you have superior opening/middle game skills than your opponent.