Some General Questions

I would feed him as much as he would eat within 15 minutes as John recommends for pyxies.
The 90 degree thing sounds a bit off but maybe He's just weary of his new surroundings.
My frogs don't really have a steady breathing pattern like humans do. I don't think it's anything to worry about.

I've noticed my guys doing the quick 90 degree turns when they are still hungry and are looking for food. My ornate pacman does this more then any of the others, but sure enough after some more food and a fuller belly he chills.

How big is your little guy?

With my feedings I started by throwing in a good amount of crickets in at night and then pulled the left overs out in the morning and counted how many they didn't eat. I used the number of many they ate to determine how many to throw in with them as a base number. I then adjust the number based on how their body weight looks, if they any or a lot of left overs, and if they have grown.

I don't feed them daily, but it's probably a good idea to do at first until you get a better idea of what your specific frogs feedings will be. Currently mine are being fed every 2-3 days and they generally eat the whole amount I put in, with occasionally 1 - 3 crickets left. I also give them other "treats" on top of the crickets as well, such as worms.

I would suggest keeping track of their feedings and mainly adjust it based on how they react and make sure they aren't looking to thin or morbidly obese.

Would love to see pictures of your pacman if you have some!