Someone who is open sexually would most likely need the attention more often than not. If you cannot give 100% to a relationship then you might need to let go of the open sexuality (assuming you mean open to experimentation?). You are clearly a good person for putting the kid first and maintaining the importance of steady income so that is a plus on your side. You could try finding a single parents kind of group so you can find someone who understands your plight and can give you more of what you need because they would need similar things.

I would imagine your best bet is casual acquaintances for mutual benefits.

Polyamory.

By starting out saying that you can’t give 100% to a relationship, you are probably eliminating partners who would want the kind of monogamous relationship you seek. You have a full life and existing obligations, so a relationship can’t be your only priority and that is totally reasonable in adult relationships. But if you want to find a loving, faithful partner, you will have to be willing to give your best to your partner. That does not mean 100% of your time, energy, or attention, but 100% of what you can.

When you are the Problem... the solution is in You.

Date someone who scares you. I heard that, or read that somewhere. Someone of some significance had given that advice to someone.

Sadly you have to put work in to find people. I get it can be hard, but try looking for friends over romance in a partner, it lends to being less likely to be cheated on.

Join the club. It kind of reminds me of when people say, "Is that too much to ask for?". Probably lol

@Kimbas' answer is the one you should be looking at - my question to you is Why do you feel you have to exclude your new partner from your family life with your son?

So if I understand you correctly , you want someone who will be available for you to have sex with , when you want it , who will not have sex with anyone else , but has no need of you , until you happen to show up ?

Reality is no woman who is open sexually and independent is going to sit around waiting for you to have time for them, they are going to get on with enjoying life. Why would they? You're not giving 100%, you're not there for them, only someone with low self esteem is going to accept that gig and then they are not going to be independent.
Either you wait until your son is older or you have to be open to include a new woman in your family life, because nobody is going to give their all when all they are getting is leftovers.

To answer your question, it's damned hard to find all those things that you say you want.
I don't know too many people, male or female, who are willing to accept any partner not giving 100% to the relationship, regardless of what else they've got going on.
No one wants to feel like an afterthought.

That's a tough situation. Part if me says to just not worry about a relationship right now. If you aren't able to make a real investment in a relationship then it might be best to just try to find a woman (or two) that you can enjoy a casual platonic friendship with. I just lost a really great relationship for very similar reasons. I feel like it was a stupid reason to split, but it was important to her, I just couldn't meet her needs in that department.