This “situationship” (because I don’t think it even sounds like a basic, compatible, mutually respectful friendship - never mind relationship) is stifling.
Neither of you are getting want you want out of it today and your visions of the future are divergent.
Why all the questions about understanding or speculating on his motivations?
What will it matter when you find out an “answer” that suits your “hunch” - is that what you need to motivate you to finally leave? Or justify your decision? Do you need permission from random strangers on in the internet to attend to the real feelings in your gut?
Why not just cut to the chase?
If you are confused, suspicious, resistant etc - it means you don’t trust - simple - no trust no relationship.
You don’t need concrete proof for your lack of trust (ie uncovering a will or financial plan to extort you) - you already have your gut.
There is nothing in this situationship of any value - no respect, no fun, no aspirations, no sex - only negativity.
Get some professional help to understand why you are stuck with this character when you and everyone else can see that he doesn’t and didn’t meet your needs (financial, emotional, maternal, aspirational, lifestyle) in any way, shape or form.
What’s your relationship history?