This is pretty good, although a lot of it is diction (word usage) rather than grammar.
The most common mistake with “who/whom” occurs when “who” is the subject of a dependent clause and so should remain “who,” even though a prepostion may occur somewhere before it. “He gave it to the man who was holding the sign.” A lot of people incorrectly make that one “whom.”
Also, in common usage “nauseous” now means “nauseated.” Usually I go with the older, more traditional meaning, but in my experience this one is now perfectly okay.
I find the most frequent grammatical lapses to be lack of parallel and the dangling modier. Lack of parallel: “Add salt, sugar, and stir.” Dangler: “After twelve years as an engineer, it was still possible for him to make mistakes.”
modifier