It sounds like he needs to be disciplined when he disobeys. Just a smack on the hand and a firm “NO” should get his attention. Then you can redirect him to something else. If he disobeys again, another “NO” and a smack on the hand. It’s ok if he cries. He will learn to obey you — and that will be especially important when you’re telling him no because he’s endangering himself or someone else!

I do agree with other people that you shouldn’t say no unless you really mean it. But if you do say no and then never follow up with any kind of consequences, it’s no wonder he keeps doing the same things. :) He’s too young to listen to reason; he just needs to obey you at this point. For example, you don’t need to say “Don’t jump off the step because you might hurt yourself.” Just say, “Jasper, do not get on the step.” Then take him off it. If he gets back on, swat his hand and say “NO.” As he gets older you can explain yourself more and more. But I do think it’s important that, at a young age, he is willing to obey you. It will set a good stage for the many fun years of parenting ahead of you! :)

All that said, good luck! He’s so precious. The pictures are adorable!