Hello, I'd like to help you with your question.
While there is no way to say for sure what someone intends on doing with their behavior, the actions you listed give a good indication that without intervention, your partner will probably end up hurting you in the same way he always has if not worse.
Some of the behaviors you listed are forgivable on their own, if your partner was willing to see what he did
as wrong as asked for forgiveness. Things such as smoking pot, while not a great choice, could be worked out if he got treatment and was willing to see it as an issue. However, actions such as installing cameras in your home, going through your drawers, hiding other relationships while engaged (or even not engaged) to you and lying to you are anti social behaviors which tell you a lot about his personality. These behaviors come from his belief that it is ok to do these things to someone you love. They could also be rooted in a personality disorder and if that is the case, only therapy and a willingness to work on these issues would help him change how he acts with you.
Some of his behavior also leans towards abusive. Being upset about you seeing your friends and spying on you are both behaviors that try to control and restrict you as a person. If you would marry him, the chances that his behavior would get worse are high. Many abusers work slowly in order to get you used to being treated badly until you question your rights as a person and by then, it is very hard to leave the relationship.
You may want to start dealing with this by learning more about abusive and anti social type behaviors which include lying, cheating, drug use and spying on you. Here are some resources that can help:
You may also want to consider therapy for yourself for the support and to decide how you want to deal with this relationship. A therapist can help you sort out your feelings about his behaviors and support you while you decide what you want to do. Just the fact that you are concerned is enough to treat this as serious.
I hope this has helped you,