The source for the "ring of bruising" phrase was Dr Perry directly to Harold Weisberg in an interview conducted at Parkland in 1966. It's in the Post Mortem book and likely on an audiotape at wherever the Weisberg materials are housed. Perry didn't just glance at the wound, he got a close look and wiped blood off the wound with his finger. Weisberg didn't push him for a conclusion, just asked some questions. Weisberg commented that Perry didn't appear to be aware of the significance of this comment. As I said, this is all from memory and its been some time since I actually re-read those pages.
As to those fragments in the throat, I have no idea. There was a reason for the throat gash... to start disposing of evidence contrary to any shots other than from the rear. Where did those fragments come from, what happened to all the other bullets, fragments, photos, xrays, evidence that are missing?? The greatest mystery to me has always been what projectile caused the throat wound are where did it originate from. I've been to Dealey Plaza twice and imo it did not come from behind the picket fence.