Like I said donation is optional it will only affect reaction :)
Nailing nipples is of course ok (thats whey there is hammer for, but there are no nails so you have to improvise LOL)
And for the limits in general use common sense if you came to the church as tourist and found this .
I am sure you would not start cutting off her nipples or try to decapitate her with your pocket knife to take head as souvenir.
also in general this is parody of this setting
except that sand is replaced with something esle