A couple of points to note when checking scale length.

1) You really want to use a solid, not a flexible rule, and certainly don't use the very end of a flexible rule as the end metal 'hook' is just riveted on in roughly the right position and can move about a lot. So its very easy to be 1mm out, or even 2mm out if it's a well used rule and the rivets have elongated their fixing holes. If you have to use a flexible rule, them don't use the end, but another marker along the rule as the start point. I normally use the 1" or 10cm position (depending on my units of measurement) to make any offset calcs easy.

2) Use the top/treble E nut slot to top/treble E saddle to measure the overall length, especially with a tune-o-matic style bridge which is almost always installed at a slight angle, so the low E is furthest away from the nut. The top E will always have the shortest overall length once its intonated, which will normally end up about 1-1.5mm longer than the nominal scale length. So it's normal to just check for the high E string position.

If you are using pickup rings, rather than thinking of mounting the pickups direct to the body, then the end of the fretboard will need to be moved back very slightly from the edge of the pickup rout so that the edge of the ring can just sit on the body, otherwise you'll get a visible gap line between the ring and the front of the rout.

It's normal for the intonation screws on the ABR-1 tune-o-matic style bridge to face forwards towards the pickups. The bridge can be installed either way round, but with the screws facing backwards, as they sit high up, the strings can catch them on the way down to the stop tail piece, and you don't want that. The string proximity to the screw also makes them quite hard to access. You can raise the stop tail piece height to stop that happening, but then you reduce the string break angle over the saddles, and you don't want that too shallow. So the screws are normally set facing the pickups. Otherwise the bridge works just as well either way round.

You can always easily turn the saddles round on an ABR-1 type bridge. This can give you an extra 1mm of adjustment, depending on which way they face to start with.

On a Nashville style tune-o-matic, the screws are smaller and are lower down from the top of the bridge, so are normally set facing backwards.