I am primary caregiver for my niece since she was 10 months and she is now 4 years old. I had no problems in potty training her. You have to be consistent and very attentive to when they need to go. Every morning I would take her to the potty, and several times during the day would just sit her there and just before she went to bed at night. As far and pooping, normally children will go around the same time daily (take note of the time) and she would hide behind a door or curtain so I knew she had to go and would immediately take her and sit her on the pot and really only had one accident once I started training her.
Yes children are more prone to act out with their mothers or primary care givers. She was as good as gold this weekend because we had company. I believe a lot their acting out is out of boredom and seeking attention, because she was playing with my other niece the weekend who is around her age and that kept her busy. But as soon as they left she started to test me because I was busy doing other things and she no longer had a playmate.
I agree that you son is seeking attention and he will do what he has to even if it is bad, such as smearing poop.
Try to make sure he always has something to do. My niece love coloring,
finger paints, coloring. Most of these activities, I sit in the floor and do with her.
I take care of my Mother who is 95 and my niece is always with me even when I'm cooking, washing clothes, etc. (I sit her near me and talk to her).
I really don't think is anything wrong with your son from what you have described as I see some things he is doing that my niece has done. Most children are just stubborn. I still at times have to pull at my niece because she won't do what I tell her. She also talked late but is getting better every day. I notice her sentence structure is better when her cousin comes for a few days.
You might find these videos helpful:
http://www.monkeysee.com/play/14663-children-listening-of...