Moving along nicely Fatboy!

Question please - does anyone shield the back of the scratch plate and similarly
the large cavity where the controls go ?
That could be a bugger as the tape has a mind of its own.
Yes and yes. For the back of the pickguard, I would suggest running the tape from the area over the control cavity right up to the the area over the neck pickup cavity. This will complete the Faraday Cage concept you're try to achieve. (think of it as 3 copper boxes that are connected)

Just like with the pickup cavities, you want to extend a bit of tape from the side of the control cavity route to the body top so there is continuity from the cavities to the pickguard.

Doing the back of a pickguard is easier than fiddling inside pickup routes because it's all flat. Don't peel all the backing off at once. peel back enough so you can stick it to your starting point, then peel it off as you lay it down in one fluid operation. It helps using a credit card or similar as a "squeegee" to flatten the tape out as you go, IYKWIM.

As for the 2 pin connectors, I've never used them, but if they're small enough and insulated, they should be fine.
They shouldn't introduce any noise. Some pickup manufacturers are now selling "solderless" pickups that use a mechanical connection in lieu of soldered.