Hi. I am not a police officer, however, based on the very limited knowledge I do have when it comes to backgrounds such as yours, it's often very standard.
To my knowledge, almost every police agency will automatically disqualify you for the use of hallucinogens. Aside from that, the selling of narcotics (felony) is probably going to be an auto-dq with probably every agency out there as well.
The tickets, alcohol violation and marijuana (if it was in the experimental range) are all things that I believe most agencies would have overlooked with the passage of some time and positives.
Sorry to say (you wanted honesty) I don't think a job as a law enforcement officer is realistic for you. Unfortunately some mistakes we make in the past stick with us, hopefully we learn from them and move on. My advice to you is to look for another career. However, maybe 10 years down the road, when you have a stable job, maybe a family, you can put in an application and see where it goes.
Please do not take my advice as a selling point for your future endeavors. I do not think you should base your aspirations and goals upon what people on a forum tell you. We can only dispel advice from knowledge (myself) or experience (a sworn LEO). If you still would like to apply, go ahead, the worst they can say is no.
Good luck in all your future endeavors.