Collaboration (PA)

Hi Coaches,
I have this question about collaboration that I am struggling a bit to coach myself on.
This PT that I’ve worked for him 3 years ago approached me offering a collaboration with me as a Nutritional Therapist & Health Coach. We stopped talking 3 years ago because he wasn’t paying me and I felt he was taking the piss ( I didn’t know about the model back then)
So we met and agreed in working together, we created a plan, agreed in how would work, the price, the duration and the starting date.
When it was close to the starting date he decided to change everything, which for me it was unprofessional. Changed the date, the price, and the duration. Created all the marketing material, sent to him, but there is no one buying the program. He always says he is busy and giving excuses, but also says that he is doing his bit, which I don’t believe. Anyway, Apart of that, he has other plans in involving me in other areas of his business to work along side each other, where I wouldn’t get paid and working with people that are not my niche at all.
I am thinking and not working with him anymore because of many reasons. But I’m afraid to miss out a good opportunity next year.
Can’t seem to be clear with my thoughts enough to make a decision.
My question is about the possibilities. Because he has this contract with an organization that he wants me to take the nutrition area of it working with kids and their families, and my niche are women with no kids with emotional eating issues. Totally different.
I’m finding difficult to watch my thoughts and put in a model. I have a new business and I want to grow, but I want to work with different people that he is offering me.