The mother is mentally unfit.

Several weeks back my, as of now, wife and myself got into an argument about a T.V. being on at night in our room. This argument eventually led to my wife leaving at 1:30am with my son. Now during this time there was a really bad storm going on,there was flooding going on and flash flood warnings poping up all over the place and she completely disreguarded this as well as me urging her to let him stay. I tried calling my mother to get her to persuade her mother to make my wife change her mind about what she was doing and her mother simply encouraged it. Just recently my son was diagnosed with the flu and his fever was up and down constantly with the alternating of childrens motrin and childrens tylenol. Even with these circumstances she still chose to listen to the advice of her sister and take him out of the house to a football game. Even with me urging her to let him stay at the house with me, she would not listen, her mother again did nothing but encourage her actions. The police were called by me and I was not even permitted to file a statement or report. Not to long ago my wife was sent to a mental hospital on a 10-13 because of answers she had given to the phsycologist during an evaluation for mental health services. While she was there she was diagnosed with depression and given a perscription for sleeping meds. and something for her depression and she doesnt take it. Everytime we have argued she makes sure that she puts our son in her arms, and she goes off on these wild tangents whenever the slightest things frustrate her. It got to the point once where she threw all of my possesions all over the front of my job which in turned got me fired later on. What do I do to at least get temporary custody of my child because he is not being raised right by her.

File an ex parte emergency temporary custody motion with the courts.

Yep, ex parte is the way to go. Do it right away. The longer you wait the less likely you will have a chance at being successful.