Panel 6: Blake “mistaking [Veidt] for a criminal” is a typical trope of superhero comics – one of the many that Moore & Gibbons circumvent in Watchmen.
Panel 7: Couple this knowledge of the Comedian’s whereabouts on the day Kennedy was killed with the off-hand remark he made during the flashback in Chapter IX, Page 20, panel 5 and it is safe to assume that the Comedian – even if he did not pull the trigger – was integral in the death of JFK, in this reality.
Panel 9: The quote Veidt offers here is indeed from President Kennedy’s intended speech on November 22, 1963. The images on the screens in front of Veidt, in this flashback, are scenes from the parade that day. It is also worth noting that the reason Veidt only has three television sets at this juncture is because there were only three stations at the time JFK was assassinated. This would also be the reason why Veidt is recording his findings on a phonograph.
Note that the clock in the background is, once again, at the “minutes to midnight” position.
And finally, note the young cat at Veidt’s feet. This is possibly a very young Bubastis, or a precursor to the genetic breakthrough that created Bubastis, or possibly just a simple cat, revered in Egypt and at home with Veidt, who feels a strong connection to ancient Egypt, as we have seen throughout the story.