My ex has HIV and uses it to stop me from Child Custody Battle?

My ex doesn't believe in divorce and in separation. We are now separated for 2 years, but still live in the same house, and he wants us to continue living together until the child grows up. Although he pays for the house, my ex is spends 85% percent of his time on his business in Canada My ex moved his parents in as well ( against my will). They have being living with me for 1 year now. 5 months ago my ex discovered he has HIV and since that every time I am trying to bring up a question of splitting residence he starts screaming at me and telling me that I am a heartless person, who doesn't care that the father needs to be with his son, and hasn't got that many years to live. My ex thinks I have being a stupid, heartless, selfish person for wishing to obtain a custody, and that if we do divorce, he should have a right to come and visit and stay with " his son" as much as he wants, as often as he wishes. From a neutral and ethical standpoint, how can i resolve this?