I thought that this was excellent and I will very much miss Dysart's puzzles. He's brought enormous joy to many people over the years.
I agree with twit at 67 that the bit above the deleted cells seems like a bit of a stretch. However I'm 99% sure that they are the correct three letters to delete.
I don't understand the shape despite jack aubrey's hint at 70.
I think I'll highlight the whole of the path despite the fact that the preamble seems to specify that only the killer should be highlighted. It just seems neater that way so I will assume that this was overlooked in the preamble.
My only loose end is at I cannot see the wordplay for 16d, which is frustrating. A gentle hint would be greatly appreciated as always.