He's not even 4, and I'm really curious why you are so worried about academics. Children learn a lot of things through play, and teaching them facts (numbers, letters, state capitals, anything else they have to regurgitate on command) hasn't been shown to accomplish anything long-term except stress. Just because a preschooler can't recite facts and figures doesn't mean at all that he's not learning. In fact, your drilling of him is getting in the way of his learning but taking up so much of his time and making him so focused on performing to get your approval.
A child this age should be outside, and if he's doing hopscotch it should be to develop gross motor skills and not to learn numbers. He should have a wide variety of toys that have nothing to do with numbers or letters. He should be building, doing puzzles, working with a variety of textures (sand play, water play...), going on nature walks to collect leaves or pine cones or whatever is in your area), and going to parks and children's museums just to EXPERIENCE things and not to recite them to you. Inside, you should be reading TO him and not focusing on him learning the letters - read a variety of books (fiction, non-fiction) that are age appropriate and which deal with a number of subjects. He should be listening to music, dancing, playing fantasy/dress up, building blanket forts and making club houses out of refrigerator boxes (with your help of course). He should have kitchen toys and workshop toys and board games and kickballs and a tricycle.
Put aside the academics, please! I think you are right when you say you don't know how to teach him. You should learn a lot more about childhood development and how children learn EVERYTHING they need to know. A child who can recite letters/numbers but whose brain didn't develop because his parents were too focused on one tiny area of learning will eventually learn those letters/numbers and have absolutely zero idea how to use them and how to function in life.
When I was teaching, we saw all kinds of kids come into kindergarten. Some knew the alphabet, some had no clue. It didn't matter. Half the time the one who was so "brilliant" because he knew these things was the one who had to repeat kindergarten (at considerable heartache) because he didn't have the social skills or the verbal skills that come from talking about and discovering a wide variety of things. These kids get so frustrated when they get a "wrong" answer that they cannot adjust. Please, just stop and go have FUN with him - that is how he will learn the best!