procedure under TX child custody law and procedure for father to seek primary custody

Father wants custody: My fiance' is in the middle of a divorce and wants custody of his daughter because the mother in extremely unbalanced, depressed and probably bi-polar. She exhibits extreme mental instability, but is not seeing a therapist. She is getting anti-depressants from a GP. He is terrifed for the wellbeing of his daughter, but has nothing to prove her mental state other then friends and family. Her own friends have called him, stated that she's nuts. His attorney's have told him it would cost around 30,000 to pursue a full custody battle. He does not have that kind of money. If I had it, I'd give it to him. Any suggestions? - Is this your question? Add additional information