Finished! I think.
I haven't worked through the parsing of clues after the six items are cycled.
On spot placement - i have put the spot in the middle of a blank cell where crossing entries are involved - is that right? I have 4 spots on edges and 3 in blank cells. This leaves all real words i believe.
I think i have the change and the deletion correct, but neither are satisfying - that is, they don't seem as complete as a the rest of the puzzle.
The puzzle itself was a great challenge, revealing itself slowly to me!