My ASD Child

My son has a new diagnosis of Asperger's.  I saw your informative video on tantrums vs meltdowns recently and it really helped me understand what was going on with my 5 year old a couple weeks ago when he had a meltdown in Target over a toy he had decided he was not leaving the store without. I refused to buy it (was $50) so the meltdown began and rocked on in the store back and forth for about an hour. This child is so strong already. I could not physically remove him from the store. (Kicking and hitting me). Of course, I was at the store alone with him. I persevered though. He wore himself down enough to finally cooperate. I also see very specific instructions regarding meltdowns on the website, which I will soon memorize. My other big problem is he is very defiant at times and totally refuses to potty train. Is this typical of Asperger's children?  Can you recommend an approach. I have tried taking pullups away, making  him sit on the potty, the reward system is a joke to hi