First of all, judging from the fight Vegeta vs Zarbon, supposing Zarbon's power is indeed over 22.000 (say, 22.500), one needs even less than 10% an advantage to stomp their opponent. Applying that rule to the BODB gaps, we have...
Farmer- 5
Martial artists- 5.5
Mr Satan- 6
Midweight champions- 6.5
Heavyweight champions- 7
Orangutans- 7
Lions- 8
Tigers- 8.5
Bears- 9.5
Now, considering Goku struggled to lift a car, he doesn't have to be much above a normal bear. I bet that if a real-life bear was shrinked to Goku's size, retained its power, got human hands, and went under a car, it could barely lift it over its shoulders too. As for the Bear Thief, who can obviously lift a car easily, he has a higher power level, but his buff body slows him down, the same way as in the fight USSJ Trunks vs Cell.
So, to complete the list...
Farmer- 5
Martial artists- 5.5
Mr Satan- 6
Midweight champions- 6.5
Heavyweight champions- 7
Orangutans- 7
Lions- 8
Tigers- 8.5
Bears- 9.5
Goku- 10
Bear Thief- 12
Farmer- 5
Martial artists- 5.5
Mr Satan- 6
Midweight champions- 6.5
Heavyweight champions- 7
Orangutans- 7
Lions- 8
Tigers- 8.5
Bears- 9.5
Now, considering Goku struggled to lift a car, he doesn't have to be much above a normal bear. I bet that if a real-life bear was shrinked to Goku's size, retained its power, got human hands, and went under a car, it could barely lift it over its shoulders too. As for the Bear Thief, who can obviously lift a car easily, he has a higher power level, but his buff body slows him down, the same way as in the fight USSJ Trunks vs Cell.
So, to complete the list...
Farmer- 5
Martial artists- 5.5
Mr Satan- 6
Midweight champions- 6.5
Heavyweight champions- 7
Orangutans- 7
Lions- 8
Tigers- 8.5
Bears- 9.5
Goku- 10
Bear Thief- 12