Beer Baron wrote: You should think about what it is about the situation that really bothers you. Figure out what of your concerns are legitimate and which aren't. I would sit down with Pat and discuss your genuine concerns with them. Perhaps even sit down with Alex and discuss your concerns. Do not be accusatory or judgmental (especially towards Alex directly). Air your concerns respectfully. Something like "I know addiction is a medical condition. I appreciate that [you/Alex] are trying to get your life in order and do things right. The way [you/Alex] treated [Pat/you] back when you were using was wrong. I care about [Pat/you] and do not want to see that pattern start again. If I do see signs of abuse, I intend to call that out."
Came here to say that ^
For me, I generally see addiction as addiction and the substance being abused becomes secondary. One alcoholic I had to live with was so much worse than any of the druggies I hung out with afterwards that I'd probably prefer the heroin addict.
It all comes down to what you want and why. As long as you're honest with yourself and with Pat/Alex, I dont think there's really a wrong answer to this one. I dont think anyone can really fault you for viewing an abusive partner of someone you care about with a suspicious eye.