When Howard bowls his make-up frame the following evening, his practice shots are edited out-of-sequence. The bowling takes place on AMF Streamlane equipment, featuring the triangular "Pindicator" on the panel above the pins. A Pindicator shows what pins are still standing after the first ball. On the first throw, all ten pins are lit. On the second throw, the Pindicator is blank. This sequence should have been edited the other way around.
In the "Floyd's Barbershop" episode the town temporarily goes into minor chaos by not having a barber shop. People had to try to cut their own hair, and the men had no place to loaf and play checkers. In this episode Emmett has taken over Floyd's old shop, but nothing is ever mentioned about where the town now gets its haircuts, nor is there any town checker-playing beyond Goober, Howard, and Andy. At the end of the series Goober does mention a new barber in town, which would have had the town in trouble for some time.
If you have bowled 8 strikes in a row you have 2 frames left, not 4.
While it's true there are ten frames in a game of bowling, it takes twelve straight strikes to complete a perfect game of 300. That's why Andy's comment that Howard is 2/3s of the way to a perfect game after eight frames is correct.