I think the kit glue is Titebond. It's what I'd use (the original red label stuff, not the more waterproof II or III versions).

Don't worry too much about measuring the scale length. You'll want to position the end of the neck slightly back from the front edge of the neck pickup pickup rout so that there's a very small ledge of about 0-5mm-1mm for the pickup ring to rest on.

Any further away from the rout and the neck will be too far forward for the scale length and you'll probably find either the rear of the pickup ring leaves a gap on the rear edge of the rout, or else you will have a gap between the neck and the pickup rig where you can see down into the neck pocket.

Too near the neck pickup rout and you'll have no ledge for the pickup ring to rest on and you'll have a gap where you can see down into the cavity.

Also, with the pickup fixed to the pickup ring, there is only a small amount of back and forwards movement available before the pickup hits the cavity walls. You don't want the pickup to touch the walls as it makes height adjustment awkward and the pickup becomes angled.

The EX kits seem to have their bridge post holes well positioned, so you shouldn't have any issues with scale length, and the bridge saddle movement should be enough to intonate the strings correctly.

If there is a noticeable thickness of paint around the neck cavity lips, say 0.5mm, then by all means get some P600 on a flat block and sand it back a bit. It's good to have the finish just running over the corners from the top and sides a sit helps the finish to stick and not chip off in those areas, but you don't need a thick bead.

"Sanding the neck pocket rather than the heel" is not about this situation, but if there's a need to adjust the neck angle slightly. And that was someone's personal view and there are good arguments for and against sanding the base of the pocket rather than the bottom of the heel. In that situation making an angled shim is probably safer that either heel or pocket sanding.

You'll find that the glue works surprisingly well as a lubricant before it starts to dry, so with glue applied to both the neck and the pocket glue areas (I use a small brush), you should find it pretty easy to slide the neck backwards and forwards slightly. As Trevor says, there will be a fair bit of excess glue squeezed out, so wipe as much off as you can quickly with a damp cloth, clamp the neck down tightly, and then go back and remove the stuff that's remaining. Don't worry too much about glue within the pickup rout, though certainty wipe away as much excess as you can for neatness, but concentrate on the visible joins. I often use a small wet paintbrush to remove glue in areas hard to reach with a cloth due to clamps getting in the way.

You'll want to clamp the tenon in the pickup rout and the end of the fretboard with separate clamps. I always use a block of 4mm MDF on the back of the body and smaller blocks of that on the neck and the tenon. You shouldn't apply the clamps directly, even if they do have rubber feet, as the body wood is very easy to mark and it does help if the clamping force is spread out as much as possible.

If it's possible for you to saw out notches in the neck clamp block that fit over the frets, then do so, as it's better for the neck clamp pressure to be applied direct to the fretboards than the frets. A lot of pressure in the middle of the frets can force the middle of the frets down and the end of the frets up, which is a bad thing.

Clamp it pretty tightly, but not excessively so, as it's possible to squeeze out too much glue and have a weak joint as a result.

Leave it clamped for 24 hours (Titebond's website recommendation for a stressed joint) and then leave it alone for another 24 hours. Don't hang it up by the neck or put any stress on the neck until this period is over.

One further point to mention (as I've talked about pickup rings and it reminded me). Look in the bridge pickup cavity and you'll see the exit hole for the pickup leads to run to the control cavity. This hole is directly under where one of the pickup ring holes will sit and is not far beneath it. As the bridge pickup ring is taller than the neck pickup ring, it comes supplied with longer screws, though disproportionately longer for the minimal extra height.

It is very easy to push the pickup leads through, then screw the pickup ring on and screw through one or both of the pickup leads.

I normally a) swap a shorter screw from the neck pickup ring with the long one from this location (provided it has enough length to screw in by a few mm) and b) attack the hole with a mixture of drill and a small Dremel sanding drum to get the initial hole entry as low as possible which i) gets the cables further away from the screw and ii) helps avoid getting the cables stuck between the pickup and the cavity wall, preventing adjustment of the pickup and tilting it at the same time.

If the shorter pickup ring screw is too short to get a decent purchase in the body, you can also fit the long screw (always drill a pilot hole first) with the pickup cables removed for the hole, withdraw it, cut the end off so that it's just shy of the cable hole and refit it.