I totally understand what you're going through. I've been in the same boat. I'm hardcore into all things mountain biking, which continues to be surrounded by a pretty masculine and intense culture. Quite the incongruity with ABDL.
I think I did more harm than good when I tried to separate my ABDL side from the rest my self, like the sort of "split personality" you mentioned, particularly because it didn't seem compatible with my other goals and interests. Once I moved towards embracing it more and realized there's really nothing wrong with it (which did take quite a while) I've been a lot happier, and don't really purge anymore either.
I'll never let it cross over into some things like mountain biking, but I found one thing that helped me accept it as part of just "me" rather than a separate personality, etc. was just letting my ABDL side flow into other things, as it suits me. For example if I'm tired at the end of the day, a cute pair of pajamas and a diaper can help me relax, and going about adult responsibilities at home in the evening like that seems to work when I'm in the mood. (Everything doesn't have to just be "littlespace" or full-on ABDL time which for me is difficult to get.)
One suggestion as well if you're having trouble with purging, is to have a Tupperware bin, duffle bag, suitcase, etc. that you can just tuck your ABDL stuff into when you want to get rid of it and shove it deep in the back of a closet somewhere. You will want it again, and if you realize that, even if you can't stop purging entirely, you can temporarily get rid of it and get away from it. I know that works for some people.