So you want something extreme, huh?
Well, with your likes and limits ONE extreme thing is obvious, so you could do that:
Clean yourself out thoroughly with large volume enemas. After you are clean, tape your penis down sissy, and give yourself another large volume enema.
At least 2-3 quarts. Plug yourself up, and get into 3 thick, or 4 thin diapers. Put slits in the inner ones beforehand.
Now you need to go outside until you have released the enema into the diaper.
If you release before you are outside, you will need to spend half an hour in a public place in those diapers.
Good luck ^^
I know it will be hard to give me a dare with my limits, but i won't complain if it's not ALL that hardcore