Sounds to me that learning ways to distract and redirection might help you more easily manage his behaviour. You've found that counting gets him moving. I suggest that you start your request with counting instead of waiting until he's not doing what you asked. Johnny, please pick up this toy or these few toys. Put them in that box. Let's see if you can get that done by the time I count 10. Then count slowly as long as he's moving. If he gets distracted, help him refocus with a gentle teminder. This trains him so that eventually he can do this on his own.
When you want him to stop doing something, also tell him what he can do. Provide more loving and positive structure in a consistent way so that he can learn what to do. Remember that negative attention is better than no attention.
How much time do you spend with him doing fun things? I suggest you've gotten into a negative pattern in your interaction with him. It's understandable because he is pushing your buttons and is difficult to manage. I urge you to find a way to let go of your irritation and become his partner in helping him learn better behaviour. He needs loving consistent structure from you and other caretakers. Know it will take time to turn this around. I suggest reading about ways to parent will be helpful. I especially like Parenting With Love And Logic by Foster Cline and others as well as books by Jane Nelson.
As to pushing your buttons, all kids are good at finding mom's buttons. Learning your buttons and diffusing them is the only way you can stop his success when pushing your buttons. He doesn't even know what buttons are or why he pushes them. He's just a kid. Buttons are complex and difficult for adults to understand.
Begin by listing your buttons and what actions activate them. I needed a counselor's support while I worked on this. I realized one important button for me was feeling challenged and frustrated when my teen daughter said some things using an attitude and tone of voice. I focused on getting her to stop with the attitude. I was unable to change her attitude by demanding she be respectful. We argued often. This lasted into her adult years. With counseling, I internalized the concept that I can't change her but I can change myself. I started noticing how my response to her increased her attitude.
My 15 yo granddaughter is living with me. My focus has been to treat her with respect. I take time to listen to her. I focus on finding ways for the two of us to resolve an issue. Because I've worked on reducing the strength my buttons have for me, I'm able to remain calm and open to discussion most of the time. A part of that work was building confidence in knowing I am in charge; that she can only get me to respond in an angry way when I let her. I am in charge of how I react.
A large part of this adjustment involved accepting that everyone is doing the best we can at any given time. We will be more successful in our responses when we accept that we and the people with whom we Interact are doing the best we can and that we can do better once we have more confidence and more information and practice. When we allow someone to push our buttons we feel defeated and unable to cope.
Your son is giving you good information when he says he wants to do better but he's unable to do better. He is asking for your help. Teach him how to do better by learning a different way to respond. Praise him when he behaves. Downplay misbehavior by telling him you know he will do better. This is an incentive for him to do better. Guide him in ways that teach skills. Distract and refocus is a skill for you to learn so that you are modeling doing that for him. We can be our children's best teachers as we learn new skills to use with them.