Pavel,
Your collimation, with CCDI error measurements between 2.9" and 4.6", is good, but not quite as good as Jim Fly's tools can make it. You should aim for 2" or less.
Maybe it's my eyes, but I still see nothing amiss with your diff spikes. I zoomed in and put a straight-edge on the screen. Looks to me like they line up.
Myself, I try to avoid huge bright stars in imaging. They're distracting.
Bob