The Sherlock Holmes professor is shot at his study door and collapses there. He is later found dead on the floor in the middle of the large study. There were no signs that he had been dragged there.
Jennifer is shown driving and leaving a message for her husband about picking up dinner and when she'll be home. When first shown driving, she's driving the older model Ford Edge. When she pulls up in to park, she's driving the newer (2015) model year.
Both Jennifer and Lynwood miss a big clue in Henley's death. He obviously fell when he died, yet the cocktail glass with the whiskey in it was upright with liqueur in it. Jennifer even picks the glass up and sniffs it but misses the obvious.
Jennifer should know how to search the internet better than she did when she first couldn't find any results for nicotine used as a murder weapon in mystery stories. A quick Google search came back with Agatha Christie's "Three Act Tragedy" as the first result.
It would be impossible to use a magnifying glass to start a fire through a frosted window. The sun simply is not strong enough through such a thick pane for this to be plausible.