If the PM told you over the phone the lease extension for the property in question got signed, and you have no doubt that was the case and not a misunderstanding with the other properties I understand she's managing for you, she outright lied to you and you need to fire her right away.

I doubt there are reliable statistics anywhere on this.

Also wanted to ask once I know how much I’m approved for (I doubt I will be approved for the full asking price of $450,000) I planned to hopefully agree to some seller financing.

But I doubt it.

It try to to that after you've closed you're opening up a much bigger can of worms than the issue of doubt transfer tax.

I doubt it's what you're looking for though. 

I also had to let go of a few other helpers along the way and am close to firing the front porch cement guy.

You almost knew without any doubt that they would be forced to sell for less than they are asking at that point.

If still in doubt, refer back to rule #3.

I doubt they will but its worth asking.