personally I would've stopped after the first message.
either he's too busy to respond, or they're not going to hire you. continuing just makes you look like a crazy person.
on a different note there are a few alarm bells going off for me, small startup business (okay not a major issue), "got to get some money sorted" who interviews before knowing what budget they have, who seriously finishes an interview with a fist bump..
This was pretty much my first introduction to the world of work - small basically startup company that was waiting on a government contract before finalising new hires - day before I was due to start the MD/owner did a runner with the money.