The first section needs 17 punctuation marks, i can only 15 and they are probably wrong

This device blocks an opening along the base/floor of stairs or other walking or working surfaces where materials or body parts might otherwise inadvertently fall through. it should be 4 inches high, with not more than ¼ inch clearance above the floor

What is wong with this sentence cameron, who has an extreme and unreasonable suspicion of other people and their motives, suffers from paranoia which is a psychological disorder characterized by delusions of persecution or grandeur, was absolutely sure that someone was following him even though he was absolutely alone and hadn't seen a car for miles and miles.

Read the following excerpt from life on the mississippi by mark twain. no girl could withstand his charms. he "cut out" every boy in the village. when his boat blew up at last, it diffused a tranquil contentment among us such as we had not known for months. but when he came home the next week, alive, renowned, and appeared in church all battered up and bandaged, a shining hero, stared at and wondered over by everybody, it seemed to us that the partiality of providence for an undeserving reptile had reached a point where it was open to criticism. how does twain's use of understatement serve his purpose? be sure to use specific details from the text to support your answer.