Cut off family member

My father is in prison for a drug crime that lead to an overdose. He is serving 24 years. We are 9 years in and I have stuck with him through this entire thing including the 4 years of court before being sent to prison. I was 14 when this happened and didnt quite understand the situation. The key factor that always stood out to me was he was 35 and the victim that OD was his girlfriend who was 18. This entire time I thought he knew what he did was wrong. That doing drugs with an 18 yr old was wrong. That dating an 18 year was wrong. I thought he regretted his decision and has learned from them. I am now realizing that is not true. He does not think he did anything wrong. Idk if I can stay by his side anymore. He has put me through a lot and im ready to cut him off. I need some opionons or advice.