The biggest difference between OCD and OCPD is that people with OCD are bothered by their symptoms, while those with OCPD are just like that, and don't tend to see any need to be different. OCPD usually bothers others around the person much more than the person who has it.

I understand that you are concerned about your dad. The thing is, you can't really change him. Personality disorders are hard to change when the person wants to change and has professional help. If the person is fine with it, there just isn't much you can do. Maybe you would do better to take a look at your own motivations and how you can cope with your dad as he is.