[Dr. Mohammad Hossein Hariri Asl]

To interpret these sentences, first you need to know about the real context where these sentences originally appeared. I searched on Google and easily found the source of these sentences.
On his website, Gerald Gillis is talking about his Uncle Jimmy who has died. Uncle Jimmy apparently had a great sense of humor because of his sizeable (large) assortment (collection) of jokes and riddles. So he was ready to use his marked witticism that he could reel off (recite or say verbally) in succession (one after each other without hesitation). So, he was quick on the trigger and ready to retort or answer back any reply or comment.
On the other hand, in spite of his great sense of humor, he was too serious about himself and about his personality or ego, he was a sensitive and fragile person who was easily hurt.