There are many reasons people get into relationships with someone much older. Some of the reasons are fine; others not so much. Whatever the initial reason, you already know that you won’t have the life you want if you stay.
It looks to me that what is keeping you stuck is that your life has become too entangled with this guy to leave him easily. You work together. He is a friend of your mother’s. And you have a strong sexual connection — which often makes it hard for people to leave a relationship. In order to leave him, you are going to have to change more than a boyfriend. You’ll need to change the way you are living your life. You may need to find another job. You may have to put boundaries on when you visit your mother, if he is often there. If you live with your mother and she wants him to spend time there, you may need to find another place to live. You will have to accept some time without sexual intimacy.
From my point of view, this is all well worth doing. You’ve already discovered that you can find a more satisfying relationship. Whether or not this one works out, you’ve given yourself that very important piece of information. That should give your self-esteem a needed boost.
You are only 28. I hope you will make the leap. You deserve to have the future you want instead of settling for what your older boyfriend offers you. If you can’t make the break, as much as you want to, consider seeing a therapist to get the support you need.
I wish you well,