My dilemma: I've showed a picture of my love interest to my friend. My friend remembers my love interest from 3 years ago when he joined in. He told me he could not tell me why but to not get involved with this man. I asked why and he said he witnessed something 3 years ago and to not let him in my life.
I don't really have any advice for you. IMO though your friend has already broken the anonymity of the program by telling you this guy is in the program. It doesn't matter if you know or not, It's none of his business. Me and my former boss went to some of the same AA meetings. The first time I saw him there we both had a look of surprise on our face. Ultimately it was his business who he told about AA and my business who I told about AA regardless if we knew other people were aware of it.
Have you given any thought that your friend has any ulterior motives for telling you to stay away from him? Have you thought about asking the guy you are interested in directly or indirectly what he was like before he got sober.
I know that in the past I have spoken in the past tense about things I did before I got sober. Not all of the time but occasionally. There is a saying that roughly goes like this: "those that fail to remember the past are doomed to repeat it".
AA/NA recommends that one should not start in a relationship until they have reached 1 year in sobriety. IMO this whole situation seems quite weird to me.