Planewave

This filter blocks everything from 300 nm up to 1200 nm - except for a "clean" solar continuum-area at 540 nm

We are very sorry, we do only offer the filters for the Canon cameras that you find on our website https://www.baader-planetarium.com/en/filters/dslr-astro-conversion.html There are no plans to produce such filters for other cameras.

It is no problem to attach the base to a round tube only with the central screw - the form of the base makes it impossible that it rotates on the telescope, and one screw is sufficient to hold the weight.
Only on a flat surface or if you can't tighten the screws, you will need two screws.

It seems that this telescope has a little problem with eye pieces of short focus lenghtes that the focuser cannot travell deep enough (in-focus).
Obviously SkyWatcher is aware of this problem, the tube of the newer models are 10mm shorter.

Okay, about our star diagonal you can find here more information according the lengthes:
https://www.baader-planetarium.com/en/blog/optical-tube-lengths-of-2-clicklock-and-bbhs-mirror-diagonals/
Maybe you can turn in the focuser fully and picture the moon on a white sheet of paper (without eye piece/ star diagonal) so you´re able to
measure the distance with a ruler to find out the back focus length.

Yes this will work. Just unscrew the visual-back and turn down fully the locking ring. Then unscrew the 2" nose piece off and turn down the
amici prism fully. Now just turn back to your appropriete position, maybe up-rigt, then turn back the locking ring to fix this position.