The thing is....his "yesterdays" IS the reason for his behavior today.
Granted, yes, he can change....ONCE he realizes it is time TO change. Once he understands that he doesn't have mommy to bail him out anymore. Once he acknowledges the fact that it is his life that HE has to account for.

As it is now, he doesn't HAVE to account for anything, especially his own behavior, because he knows that you are there to do it for him....DESPITE of what you may say or feel. It is your actions every time that tell him how it IS for him. And he relies on you to bail him out...every single time.

I can sorta relate to how difficult changing just might actually be for your son, as I was there myself in my early years. I really wasn't taught "responsibility". I knew what it was, but I hadn't a clue (then) HOW to apply it to my own life.
I was a VERY late bloomer regarding taking responsibility for my own actions. I'm really not sure why I was so irresponsible for such a long time in my younger years. There were many things which I'm sure contributed to it, but the fact was that I wasn't accepting my OWN responsibility. I had spent more energy seeking (what I thought was then) the "easy" way in life..(doing as little as I had to TO get by....getting by on the shirt tails of others, etc).
Although, I tried many times, aware that I'm supposed to be responsible, I simply struggled relentlessly with the "trial & error" of applying the necessary behavior to my own life. But the fact was that I simply wasn't taught how to utilize this behavior. VERY frustrating, exhausting AND frightening....not to mention how my inabilities only seemed to reinforce my sense of failure. It became a vicious cycle which seem to have lasted forever....(well into my early 30's).
Even though I was aware that it was my actions that I had to account for, I never really was able to apply a MUCH needed change to my behavior. I went through the motions of "trying" to do the right thing...that would last for a while, until I seemed to slip back into what was familiar to me...(what I thought was more) failing.
At some point it finally hit me and things began to fall into "play'.

My point of including this is not to excuse your son's behavior, but maybe to enlighten you from the viewpoint of where your son just may be emotionally & psychologically. It's really hard to say, but from what you have described of him, it is possible that he may be struggling as I had. Of course, there are differences of him and self (I left home in my teens...not by choice), but our struggles sound quite similar.
Regardless, the fact IS that your son HAS to deal with his struggles for his own self...otherwise he will NEVER obtain his own sense of purpose or worth.

It may sound harsh....well, to him it IS harsh and to you it feels harsh..but, as hard as it is... it is your duty as his parent to allow him the opportunity to discover his placement in his OWN life.
Allow him the opportunity to fall while you are still here to help him back to his feet. The inevitable is only being postponed at present.
(Imagine how difficult it will be for him far later in his years to go through these changes..possibly while married and with kids....imagine their struggles because of his?)...I made that mistake, and other's suffered for my inabilities.

As hard as it is, letting him go is forcing him to deal with with his own consequences. He NEEDS that TO learn his own purpose. And we all know, without a sense of purpose we only wander in an existence...a far cry from LIVING.
Forcing him is the best action you can take to show him your love for him.

I wish you both the best.

Shangrala