what a big boy!
bribing" and going bonkers with joy when he's successful is the way forward
1 smartie (or sticker star) for every wee in the potty, 2 for a poop
if he's nervous tell him it's like sneezing - mostly you get a tissue on time, sometimes you just can't bloody reach and it ends up elsewhere...no biggie
we never really did the whole potty training, DS1 couldn't be bothered and didn't like it much, we stopped after a few weeks, then he went straight on to toilet with training seat (at 3 years old)
DS2 was a chunky lad, at his first try he did a pee in the potty, but as he stood up the potty was still attached to his bottom, which freaked him out. he never sat on it again and went on the toilet some months later (around 3 as well)
from then on I never bothered with a potty, also I heard that some people struggle with the potty to toilet transition, so we skipped it altogether.
but that's me, a lot of people do it and it all good. (I still remember my pink potty, loved it!)
1 tip for boys, if his willy keeps going above the rim, sit him back to front, the back of the seat is higher so he's more likely to succeed!
good luck! 