singular,
Dame filling and "tiny ko" paper for area scoring:
http://home.snafu.de/jasiek/kodame.pdf
Counting and evaluating positions: Of course, there is Positional Judgement 1 - Territory. However, a) it is only marginally about the endgame and b) it is too demanding for your KGS 9k level. You can still do with roughly approximating multiples of 10 or 5. Note that each dead stone counts 2 points (the stone plus its intersection.)
Practising ultra-basic positions: start with your own games and multiples of 10.
How to calculate value: you find Ogawa's book above your head and are still interested in value calculation theory? I can suggest a lot, but please first clarify how serious you are in surpassing your current rank WRT to counting theory out of curiosity.
Sente versus big move: multiply sente by 2.
Damezumari: tesuji, throw-ins, capturing race theory.
Endgame start: at move 1 of the game! It proceeds in parallel to opening and middle game. Optimise your early strategy also for the later endgame.
Avoid making shapes vulnerable to tesuji: create "thick" shapes.
Which moves are endgame moves: each move. Each move has its impact on the endgame.
Ignore endgame: nnnnnnnnnooooooooo! But... you do not need all value theory yet.