Heirs and Beneficiaries: What Can One Disgruntled Heir Do

We live in Arizona. My father left a will naming me as Executor of his estate. He owned a lot of stock and when I contacted the brokerage firms they wanted the will probated because some of the brokerages had no beneficiaries named. We did that and sent the 3 other heirs everything required by the courts. Now we are waiting the 4 months before I can distribute the funds. One heir is a nephew who we have restraining orders against and has unsuccessfully sued us for $9000 claiming we have influenced his grandfather against him( our father had dementia and knew no one for the last 2 years) . It was dismissed with prejudice meaning he could not bring it up again. He also harassed me and my family and threated to watch us go to hell in a fire. The state of Arizona prosecuted him and after many state appointed attorneys, he pleaded guilty. He is now a felon on probation. One of the first things I did was send each heir. including our nephew, $95,000 from the joint account I had with my Dad. I knew this would take a long time to sell the stock and his account was over the FICA insurance so as executor I sent everyone this amount with a letter saying after the we would settle the rest of the estate after the stock was sold. Then I found out that the brokerages didn't accept the will, but wanted a court probate papers. So we took the will to court and had it probated. Now he has used his money to hire an attorney and I am wondering what this could mean. Can he appoint himself as executor? He is 28 and is a 2 year old having tantrums. His mother died at childbirth and we took care of him for 4 months. He now rants and raves about me having him circumcised. He wanted to sue us , but the attorneys at the free clinic told him it was too old. The strange part of it is that we only cared for him for 4 months and Drs. don't circumcise any baby without the parents request and permission. I honestly don't remember ever taking him to the Dr. That was 50 years ago. So he is an out of control pot head who also takes meds for mental issues.(found out in discovery) We definitely can't let him take over and what do we do if he has objections to me being the executor? How can I stop this continued harassment? He used the $9000 suit to send us harassing letters for 9 months until we appeared before a judge and it was thrown out. I think this is going to be the same trick. His probation and our protective orders don't allow any contact, but if he sues us he is free to write all the ranting letters he wants to write.
There is no other suitable person to be executor because my sister lives in Germany and my brother is too busy at work to sign the few papers I have sent him. Besides, I was his power of attorney when he found out about his dementia, so I know all about his business. In order to protect our inheritance and the estate I have to do this. If I hire an attorney what will he do>

Heirs and Beneficiaries: What Can One Disgruntled Heir Do