Returning from a hunting trip in the forest, the Henderson family's car hits an animal in the road. At first they fear it was a man, but when they examine the "body" they find it's a "bigfoot". They think it's dead so they decide to take it home (there could be some money in this). As you guessed, it isn't dead. Far from being the ferocious monster they fear "Harry" to be, he's a friendly giant.
Harry gets a cut on the back of his hand at some point when he’s tearing up the house (you don’t actually see him get cut, just the aftermath) and the Henderson’s treat the wound
When a pool cleaner scoops a bunch of Harry’s hair from a woman’s pool, he says “you don’t have a cat, do you?” implying that the giant clump of hair could be a dead cat. She says no, and he says “good, so it’s just a hairball”
No, but the Henderson’s nosy neighbor goes through their fridge at one point looking for foods she can eat on her new fad diet. It’s implied that the dieting is standard behavior for her and she’s seen exercising at least once later in the movie