In Tx, ex-wife was killed in a car accident. Both of us were joint managing conservators of our son. Am I now sole conservator?

Dec. 20, 2008 my ex-wife was killed while drinking and driving. Prior to this tragedy, my ex-wife had developed a drinking problem that led to chronic endagerment of herself and others on the road while drinking and driving. I pleaded with her mother and stepfather on several occasions to perform an intervention on her. They both made a mockery of my pleas. She was leaving our son more and more with her mother and step-father while she would go out and meet friends at various bars. They minimized her problem by stating to me, whenever I expressed concern, that she was just having fun. I witnessed my ex-wife, of which I was reuniting with, get thrown thru the windshield of her SUV hundreds of yards into the air before landing onto the street where her head was cracked open, her brain matter was splattered onto the street and her face was distorted in the most gruesome manner. For years prior to this incident, the grandparents were overly subjecting my son to materialism and the Disneyland syndrome. My ex-wife was their only child. Now, my ex-wife's mom thinks my son is her "second" chance. I am concerned that she is going to try to seek legal custody of him. While my ex-wife was alive, her parents paid for my son to go to a private school. (I was paying child support throughout). It is worth noting that they also collected a life insurance policy on my ex-wife that listed my son as beneficiary and his grandmother as the trustee. Only one week after my ex-wife's death, they contacted the Attorney General's office seeking to have my child support payments sent to them and then contacted the Social Security office seeking my ex-wife's SSI death benefit payments. At this point in time, because I work, I have agreed to drop my son off with grandparents in morning so he can resume with his school year in private school. The grandparents are and have been for years paying for my sons private school. Additionally, my son goes to their house after school until I get off work and pick him up. Some weekend days and nights I let him go over to visit so that he can go golfing. My concern is that they are keeping a timeline of my son's time spent over there in an effort to file for custody becauses he spends lots of time at their house while I'm at work and on the weekends for recreation. A few days after my wife lost her life as she did, I sought treatment for post traumatic stress from the tragedy. At the funeral service, photos of my ex-wife drinking in a bar were placed on the screen as part of the memorial service. They saw my reaction to her senseless death, coupled with grief and distress, as an avenue in which to try to take my son from me on the grounds of mental incompetency. Now, I am concerned as to whether I should minimize visitation between them and my son. Should I remove my son from private school. Should I distance me and my son from them all together. I want what is best for my son, but I don't want to be manipulated by them while they plot to take him away from me. They have threatened to fight me to the death for custody of my son. I was told that they have 90 days after the death of my ex-wife to build a case against me in an effort to state that they have provided the majority of time to my son's care. They both are heavy drinkers and smoke pot. I do not want my son, who is now 13 years old, being raised in this environment. What should I do at this point? I am confused, still processing the grief from this tragic loss and I just do not have the financial means to fight with them in court. Please advise me as to what my rights are. Thank you./ - Is this your question? Add additional information