I think "making fish" is a great idea.
My cousin is a little older than Jessie. (My aunt had kids about the same time I did, LOL!! - and I was NOT a teen mommy) Potty training was a NIGHTMARE for my controlling aunt. Abby used to chase the garbage man because he was taking her used diapers. She hid them ALL OVER the house. She also purposely peed on things when she was angry. Like my mom's car when she insisted Abby sit in a carseat. Abby had gotten to sit in the regular seat on the airplane and decided no more carseats. (That totally does not fly in our family - not with ANY of us. My stars, I sat in carseats from when they were first available!) The kid had to sit in the wet seat until they got here, over an hour drive. Then she had to help get the carseat apart and wash it!
Anyway, kids are strange about pottying. So keep up the positive, and don't worry about him. He really WILL get it.