Well, while I cannot respond to your specific questions, I can offer a little advise. I am a 52 (almost 53) year old Mom. My son was very hard to train. He had a sister a little bit less than 2 years younger.
It was very difficult to potty-train my son; why should he have to, she doesn't and so goes the story.
My daughter was "much" easier. She had a terrible diaper rash and I simply explained one morning that we would not be using diapers anymore because her bottom needed to heal. While it did take me 3 hours that morning to shower, dress, put the make-up on,etc., she did make it. She never peed in her pants during the day again. It took a couple of month to conquer the night-time pees, but not long.
By this time, of course, her brother had succeeded in both regards. My only suggestion would be to have her watch you or your husband poop in the toilet. It does seem to help a lot. While seemingly a little gross, show them how it is done.
My grandson had to have penal surgery when he was around 8 months old. He did not want his Mother or I to touch him there for quite a while. In fact, he really still doesn't like it that much; "says it tickles." This is at bathing time, so please don't get me wrong.
Let your child watch you - poop, pee, whatever. It's a bodily function that needs to be shared.
My husband taught my son how to pee in the toilet by making bubbles - how fun. They also both learned how to clean off the walls, toilet and surrounding areas; at least it worked.
Let your child watch.
In addition, don't push your boy. Let him watch his father. For whatever weird reason, boys are harder to train. The more you push, the more he will resist.
J.