Note: These are my opinions. ie, how I would do things in my game.
Addiction should be a save made with both End and Psyche. To use it with zero effects, your Psyche and End should be at least 2CS higher than the Addiction intensity of the drug. Remarkable seems like a decent intensity for something like Cocaine, while Pot would have more like a Typical Intensity.
Pot would likely give penalties to any power used on the drug user that tried to make him angry. I'd also slap a -1CS to Intuition, maybe Agility.
Cocaine would give a +1CS to Intuition (max of Remarkable) but give a -2CS penalty to all End tests when making a kill check.
Morphine gives the same penalties as Pot, but also gives a -2CS to Psyche. After a certain amount of time, that -2 to Psyche becomes permanent. (This could be applied to many drugs)
PCP would give a bonus of +1CS to Strength (Max Remarkable) but has the same penalty as cocaine. It also has the added effect of negating pain (but not damage). You might even give them like Good Iron Will.
Booze would give a pretty hefty penalty to Agility and Intuition, say maybe -2, possibly even 3 depending on how much is drunk.