K.K.
Have you tried blowing bubbles??? That might get him to sit still. Honestly at this point, i might suggest having another family member step in and take over. Could Dad take a day or grandma??? He just sounds like he knows how to make you crazy and really enjoys doing that.
Also, During potty training, that is the one time you DO want them totally filled up with fluid. maybe not walking around with a sippy cup, but offering them a beverage every 15 mins or so, even just a few sipps. I bought special juice boxes for my daughter and that was the only time she was ever allowed fruit punch which she loved.
also, it was rough, but making my daughter clean up after her accidents, by herself (well she thought so anyway) was very helpful. It wasn't a punishment, but being responsible for your actions. I never yelled at her but just kept repeating, "you need to wipe up your pee pee" and handing her the rag, and sometimes even holding that hand as she wiped. Again, not done in anger but not letting them get away with anything either.
Another thought, taking away all the other fun stuff he has in that room or that floor of the house, so that the only toys, books, attention from you is centered around the potty might help. Do you see what i mean?? taking away all distractions.
I say, keep taking him every 30 mins, but don't make him sit for more than one to two minutes unless, it is at a time you are pretty sure he needs to go.
It seems this is the season for potty training there have been so many posts lately. I loved the Potty TRaining in Just One Day program that was developed for children with disablities, there is an updated version on the web, with free charts and info even if you don't purchase the program.'
Good luck T., it seems like you are doing everything right, Take a breather and keep calm through it all, it really does pass relatively quickly