I'm going to cut my ex out of my life
What did he do to deserve no more contact?
This guy has been such a bad influence because of his drug abuse and manipulative behavior
It's usually wrong to cut someone out of your life entirely, but in this situation, you are probably justified.  It sounds like he is harmful to you, and possibly dangerous, so you would be wise to stay away.
I will lose contact with him. It's going to be strange since he's my friend and ex-boyfriend.
More power to you, you deserve a lot of happiness and to not have these bad experiences define you. I'm sure he will get the message and understand what he has done to you. You will find someone better in the end.