Half and half is simply half whole milk and half cream. In the UK, they call it half cream. According The Kitchn, half and half typically has a 10 to 12 percent fat content, which, it stands to reason, means it's less fatty than cream and fattier than milk.
Dogs can eat peas safely. Peas are a good source of potassium, zinc, iron and several vitamins. Depending on the size of the dog, 1 or 2 tablespoons of peas is recommended. The dietary fiber in peas also helps overweight dogs feel full thereby reducing the dog's intake.
If the diarrhea continues, you can try a bland diet. Boiled chicken with rice works great. You can also try adding pumpkin (100% pure canned pumpkin) to the regular food to help firm things up. In addition, yes, you can use Pepto Bismol on your dog.