Edit: ^^ That too.
He is probably adjusting to now being fed in his enclosure which is proper. Feeding outside the cage is a myth. You can also switch him to rats.
If he is striking without opening his mouth, it is a mock strike and is for defensive posturing and a warning to back off.
If you are feeding frozen/thawed mice and he doesn't eat it right away, you can leave it in there overnight. Throw the rodent out in the morning. Do not attempt feeding multiple days in a row, if the snake does not eat on its regularly scheduled day, then you can wait until its next feeding day.
Questions for you:
- How many mice are you feeding at a time?
- What is your set up like? Temperatures, humidity, enclosure type, hides?
- Do you know how big the snake is in weight? Measured in grams preferred.