When you say really small, how small is he? Do you have a scale? If not, definitely invest in one.
As for feeding, keep it at 3 days until he hits about 30 grams then you can go to 5 days. Hognoses have a much higher metabolism than other snakes. If the pinky isn't leaving any type of 'bump' then it's time to move up to the next size food. I have a boy who is on a feeding strike right now but is eating fuzzies even though it doesn't look like he should be.