Can my violent drug taking ex..

Okay. So I was with my baby's dad from august the 5th 2016 until November the 1st 2017. We lived together for 10 months and in that time lost 4 babies and caught with my current son in August. My ex partner has a history of domestic violence towards me and is known to be a very heavy cannabis user (its illegal in the UK) and has also been arrested for drug offences relating to cocaine, benzacane and cannabis which he was charged with January 2017. I had to split with him and terminate my rights to our rented house we shared in November last year after a domestic incident occurred and resulted in police and domestic violence teams involvement. I went to court for a non molestation order which was granted but later thrown out by the courts due to me not turning up for the 2nd hearing a week later (I was spreading my grandfather's ashes) he hasn't made any effort to contact me since and was wondering what rights he has to his son if I don't put his name on the birth certificate and what processes would he be able to go through to ruin mine and my sons life further or in other words gain access or custody when I obviously don't want him involved. He does go to work and lives in the property we shared with his drug using brother who lost his son in the care system last year. I want to make sure he never sees his son or even gets to hold him he's been listed as a very violent person with a history of drug, domestic violence issues, and sexual abuse including rape with me when we was 14 however it was never taken through court as my mental health wasn't able to cope at the time due to trauma. I've recently had to have counselling for the trauma I went through this year as a result of him. HELP