Give tenant a deadline in writing and spell out the consequence of violating the lease.

Miss the deadline?

While you can certainly do it, Don't become a  motivated buyer and do a bad deal just to hit an arbitrary deadline.

I started to raise my voice 2 weeks ago, this is when the things started to move, but I suspect that he missed some deadline and this is why the perfect case is in a mess now.

This is something that just came to my attention, and I'm working on a deadline. 

Should I take his inability to meet 2 deadlines as enough evidence to run for the hills and hire somebody else?  

I clear the snow for my own properties and while I generally do a pretty good job at keeping up with it, I've missed these deadlines from time to time and never once received any sort of penalty for it.  

One of the reasons I want to start with a house hack first is to, obviously, decrease rent expenses but also to buy a rehab and learn how to manage contractors and deadlines locally prior to moving OOS.

I explained to him that I have interest in other properties and gave him  a Thursday deadline  (been going on 3 weeks )We as investors can't wait forever and have limited resources. 

Well, you can . . . but when the seller finds out the cash is NOT your cash, they could pull out of the deal, and depending on your deadlines,  they could keep you earnest money.