The Loctite 648 data sheet says it's good for 6 mil = 0.15 mm gaps, a generous fit, so it should work for what you've got.
Definitely: roughen the shaft, meticulously clean shaft + pinion bore, gimmick a fixture to hold the pinon in the right position so it doesn't wobble while the adhesive cures, then apply adhesive and slide in place.
Although I loves me a good caliper, they're no good for measuring small holes. For teeny holes, use something like a set of drills to find a go/no-go pair, then guesstimate between them. A number-size drill set comes in handy, even for hard-metric holes, and is much easier to find (here in the USA, anyhow) than a metric drill set with 0.1 mm increments.