I'm with Nooner on this one: Run fast and run far.
Your biggest problem isn't the kid:
"He tries to get in between my bf and me all the time. [
]He whines and gets his way.[] (Emphasis mine.)
Kids will whine to get their way; it's been happening since the beginning of time. Your problem is that Duddy/boyfriend doesn't have a spine.
When I was single, I didn't categorically rule out dating parents, but I realized there were only about 5% I could tolerate dating.
Maybe they left Mumsie for good reason or maybe they got left, but in my experience, most single Duddies are guilt-ridden pansies with hellions in tow. No thanks.