There are some very strong and compelling aspects between the two of you.
Moons in aspect (square), same mars, and his Jupiter on your scorpio stellium that is a very feel-good attraction. Venus/mars sextile, moon opposite mercury/uranus that is mesmerising. Uranus is your descendent ruler, and his is exactly conjunct your ascendent so you see your ideal partner in him. His descendent is ruled by mercury, and your mercury is conjunct his Jupiter, ruler of his ascendent, so again a magnetic pull and you each reflect the other's needs.
These are all really strong and attractive energies that pull you towards him.
On the negative, there are a mars/pluto conjunction, a mars/uranus conjunction, both physically attractive but really volatile.
Your Neptune is on his Jupiter while his Neptune squares your Jupiter so you each manage to live a fantasy about the relationship, feeling good and expansive but it's all an illusion.
The most compelling contact though might be his moon on your north node.
Here is an explanation this contact from the cafe astrology website that explains it very well (in your case it is his moon on your node):
"When your Moon conjuncts your partner’s North Node, you will be deeply affected by your relationship. Neither of you will forget each other, as this relationship is meaningful on a deep level to you both. There are life-size themes of nurturing and safety in this relationship. The Moon person expresses qualities that the North Node person, on a subconscious level, needs to develop in order to grow spiritually. The attraction can be intense, and the relationship itself will be a distinctly emotional connection. Issues of security, taking care of each other, and protection are dominant ones in this partnership. There is an instant bond between the two of you, almost as if this relationship feels “meant to be”. The ties are strong, and the bond is hard to break. If you do part, both of you will feel attached to the memory of the relationship and the person, and if you were to meet again, you would not feel any distance between you. There is an instant attraction and sympathy between you. If there is discomfort in the relationship, it will likely come from the North Node person, as there is a sense of fatedness involved here. The Moon person may feel that he or she gives more emotionally than the North Node person at times, but will generally be comfortable with this role."
In his natal chart, he has a sun/pluto conjunction that makes him overpowering and domineering as a personality. He also has moon square Uranus making him moody, unreliable and unpredictable.
His Chiron is in your 7th house of relationships, guaranteeing that this is a painful relationship and it is square your scorpio stellium. Your Chiron is exactly on his mars, continually stirring up pain in you.
All of this is an explanation.
But now the analysis, outside the sphere of astrology, do you really want to be in this type of relationship, with a person who is not only drug dependent and sharing him with anyone in a skirt that passes by? Is this the type of partner you think you deserve? You need to reason this out and use your head, not only your heart. You deserve better.
It will be almost impossible for him to change.
You need a lot of will power, you have to believe your life should be better.
