Child custody?

i am currently going thru the court process of getting custody of my 3 1/2 year old son. My ex and i were together 4 1/2 years until he cheated i have had my son living with me for over a year now and the father has had visitation although i have stopped this as the last time he was at his father's he cam home smelling of marijauna i am also worried that he is seeing things he should not like his father being ually active with his new gf as he has been touching himself lately and he has not done it for a very long time. I don't kow if i should bring this up in court when i go or just let it go. I however am wondering if my stopping his visits could be used against me? Also his new gf recently started a argument in the courthouse with me because i was there the same time he had been there and there is a restraing order againt him for aulting me which he was convicted. Am i making the right choice here