There is a serious SERIOUS lack of research, study, literature, and books regarding the entire AB/DL world. I welcome and applaud anyone who wants to do formal work on it like this.
I did once on request of my old GF. Her discussions and feelings on how I should act about it were pretty unfair and disrespectful so I resumed in a few months.
I've come to just accept them as part of who I am along with my other fetishes. I'm actually quite proud of them and I feel them make me unique in ways not many other people are. Sure they're not widely accepted and I would easily be called a freak or gross but they make me immensely happy so I'll just keep doing what I do.
It depends on your skin, really. Some people get rashes from it faster than others. I personally can sleep in a wet diaper all night without any issues. Creams and powders will help too if you want to feel extra safe.
I tried suspenders with my plastic diapers but it tears them easily. I end up taking an elastic-rope and threading it between the tapes (or pins in your case) to make a makes-shift elastic waist-band. Tighten and tie into a knot or bow.
Works decently.
Unless your poop is really runny it generally won't run anywhere so pretty much any diaper will contain it fine. If you're running out of room then just tug the diaper down a bit while you push and then pull it back up once you're done. Or try a larger size so it's more loose.
The risk is there yes. Some creams can help prevent it as well as keeping the mess away from the front of the diaper, but there is always a risk.
Also the risk of rash is also big.
Apart from just eat pure grains there isn't much you can do. It just stinks. Plastic pants might help for awhile, but probably not 100%. A thicker diaper might help too but again, not for long.