J.,
In speaking first to the potty training matter, you want to be careful not to push him too hard in that direction. Boys especially are generally a little slower to get the hang of potty training. Pushing a child too soon adds an unnecessary layer of stress. The fact that you are noting some indications of what you are calling "OCD" could be a sign that he is feeling overly stressed out by the process because he is simply not ready. Believe me, I have studied almost all of the programs that say you can potty train your child in a day, a weekend, etc...but the reality is that you could be putting too much stress on your child.
I was under the gun with my youngest daughter to get her potty trained before preschool began. I used some of the "quick" methods and my daughter started stuttering out of the blue. I decide to lay off and let her take potty training at her own pace. The stuttering stopped within 10 days and she was trained in the next 60 days.
As for the POOP it is not unnormal for children, boys and girls, to be interested in "POOP." He is probably interested in the fact that it comes from his body and that it is something he has in common with mom, dad, the dog, etc. Absolutely drawing the line at touching it, giving him a simple explanation of why things "POOP" and why he does not want to touch it. The interest may also be a diversion tactic. If he feels like you are hounding him on the potty training he may be using the poop fascination as a means to get you to ease up.
As for OCD, please don't pre-diagnose him with anything simply because there may be (what I assume is a) diagnosed history. Young children are often fascinated with certain repeated actions such as lining up cars, dolls, eating with the same dish, etc. Most often moms recognize these a "jags" which change fairly quickly.
I wouldn't worry too much. If it were me I would just change up my tactics a little bit and I would think it will all be fine.