Basically, I'm insanely excited about this job. I interviewed for and the CFO absolutely loved me. I got the offer 2 days later and they're offering me exactly what I told my boss was what I wanted. 10k /yr more.
Your questioning should be limited to asking whether they'd prefer you sign in blue or black ink.
Even in a large, faceless company, negotiating after having your demands met on the button would go over poorly. In a small, family-run place, it would go over even worse. If you're on such a fast growth trajectory in your career, your path to more money is more contributions and more responsibility and I think it's fair to discuss THOSE topics with the CFO and owner as you begin the new role.
But, approach it as a win-win: you want to understand how success is measured and how you can best contribute to the growth and success of the company. If you feel you need to draw a line between that and your own comp, you can (though it's probably not needed), but do it from a give-to-get point of view, not a "oh, maybe I didn't ask for enough" position that will be interpreted as bad faith negotiations/greed.