Your main thesis is that Khufu is not the owner of this pyramid. By incriminating as many marks as you can you hope to cast doubt on all to prove your thesis. I bet a lot your readers take that to the bank.
Is it plausible to think that all are fakes? What was the motive of the alleged fraud and what was necessary and sufficient to perpetrate it (see Corpuscle's post)? To come home to England with a trophy in hand by plastering the chambers all over with red symbols they didn't even know? This makes no sense even for a guy who blasts himself into ancient monuments.
Casting doubt isn't proof. Even if there is one, or even a few, fake marks, it doesn't rule out Khufu as the owner of the pyramid. At a bare minimum you'd have to prove that all those pointing to Khufu are fake and even still you won't rule out Khufu as the builder of this pyramid. I have proof that Hemiunu, Khufu's vizier, designed the dimensions, angle, indent, King Chamber, and north shaft of this pyramid. Robert and I have shown that explicit proof of Khufu's ownership is probably authentic. It couldn't be more explicit: "he has built his pyramid....". The Wadi El Jarf Papyrus shows that Tura stone was shipped to Giza when Khufu and Ankhaf were in power. A sixth dynasty scribe whose tomb is steps away from the pyramid called it Khufu Akhet-Mr. In the debris of the stone quarry south of G1, Khufu's seals were found. Khufu's family members are buried around this pyramid. Khufu's predecessor built at least 8 (6 + 2) pyramids, some with features resembling Khufu Akhet.
The marks inside the chambers are not a holy grail. They are icing on a cake baked with evidence from multiple angles. You are nowhere close to felling the "Khufu-built-G1" Theory.
Against all this you are holding:
1) paint runnels and spladder marks
2) turned numerals
3) an upside down symbol gone missing in a sketch
all three of which have plausible and reasonable explanations you have not ruled out:
1) painted in situ by pyramid workers
2) painted by a different crew than the nfr and was gangs
3) a harmless mistake
But as I already pointed out...the definitive proof is the Khufu cartouche next to the one you think is fake. Until you get a permit to probe it, I wouldn't waste time casting doubts. The only people who will accept this as proof are the same people who come into this with the preformed belief that the pyramids are too technically advanced for the OK. All they need is a confirmation of their bias. Doubts cast is all they need to feel vindicated. But this is not science, Scott unless you're just trying to sell books to your base. I would devise another unequivocal test of your theory. A theory which cannot be put to the test is useless and in any case does not replace another supported by evidence. Your theory has raised some doubts about one mark in Khufu's pyramid. The next step is to actually prove it is fake.