Child custody battle in one week. Please help, my ex husband in a manipulator!?

Ok so I have court in 6 days. It is to finalise my divorce and establish custody and a parenting plan of my 18 month old son. We seperated when he was 5 months old and our son has always resisded with me. My ex has a history of drug and alcohol abuse and was just arrested 2 weeks ago for a DUI. However he is trying to get custody of my son and says he took pictures of bruises on his leg and is going to use them against me to prove me as an unfit mother. I love my son to death! I would never harm him or let anyone harm him. I work full time and he has his own room and everything he needs. I also take him to all doctor and dentist appts and cut his nails and toe nails because his dad wont do any of it. Also he did'nt want custody until he found out he was going to have to pay child support. His girlfriend is 18 years older than him and he is roomates with her son. My son would'nt even have his own room if he lived with his father. I'm a little nervous because hes a good liar and He has threatend me with those pictures ans he is having his pot head friends go to court and lie for him to say terrible things about me. What is your input? Any help would be great! Thank you.