1. Bored carb not shimmed right/air leak?
2. Carbon blocking exhaust port?
3. #70 Seems high, possibly running too rich.
4. #64 is the biggest stock, say +2 for exhaust = 66, be safe, try a 68, see how it works, than 66. if you are running no airbox, 68 for sure.
5. ?????
6. Profit!