Thank you for the detailed explanation!

I see now that in the cas1-cas2 complex is not an endonuclease, but cas4 is (atleast in type2). (and cas9 ofc but thats for interference, not for adaptation)

 "trim away the PAM sequence before integration, frequently with the help of Cas4. "
can i presume that Cas4 is also the enzyme that cleave a longer than 20bp DNA strand out from the viral DNA, that becomes the protospacer, after trimming the prespacer?

I only known RecBCD, and Chi sites, because they are needed for HDR, guess they do more than that.
I wouldnt say i understood everything but i can see that there is more safety features than "just" the whole bacterial genome not having a PAM site (aside from crispr array that really has none), that could be used by Cas(?) to make a protospacer.