I'm up to my eyeballs with the amount of money that I've had to shell out due to this massive oversight/negligence. 

Most PM contracts have a get out of jail mostly free card but this borders on gross negligence (an important distinction from simple negligence) if you could unearth that from a simple google search and you may have a case to collect. 

The difference between a 200A and a 150A is negligible.

oh and also he was supposed to provided the leases for the tenants according to the contract and he never did , is that another clause I can use to prove his negligence? 

The notice to quit was given him the right to stay in the house until October 1st, he filed an appearance on November 15th (not sure why he had a month and a half to file an appearance, I think was my attorneys negligence, but he says that is the time it takes) I am still waiting for a mediation date, but it is already 4 months he is living there for free.

Do your own numbers and measure against the numbers you are given.A poor appraisal can be reported, but you need real numbers and proof of negligence to do more that get your money back or have another agent in that company get another.Don't fall into the trap.

The PM should have cited negligence with the AC when the damage was found/corrected and invoiced them at that point. 

However, if there were no visible signs of disease and the tree was somewhat maintained (in a typical/prudent manner), then you're going to have a really hard time pinning negligence on the tree owner or getting anywhere with that approach. 

Here were the keys:  1) Got tenant to agree the damage was due to his negligence and he signed a statement to that effect.  2) Got him to sign a Promissory Note (found it online for Oklahoma and simply copied/pasted) saying he would pay the full balance due by minimum of $200 payment per month due same date as normal rent. 

I was just reading today an appellate court opinion here in Illinois where someone purchased a 2nd mortgage w/o realizing a 1st existed, then tried to reverse the CONFIRMED sale after subsequent auction on foreclosure of the 1st for a myriad of reasons, and then sued his attorney for malpractice: https://ilcourtsaudio.blob.cor...As part of the legal malpractice claim against his lawyer, the plaintiff (2nd mtg buyer) stated, "that Gooch also “negligently failed to stay the final judgment of sale during appeal, resulting in dismissal of the appeal in October 2015 as moot because no remedy remained available to reverse the sale to a third-party purchaser."