5. Previously he was offered live small rats
To me here is your main problem, you offered F/T mice to an animal that was eating Live rats.

Switching can be tricky and when done it is often better to

1# Switch a well establish snake, which means a snake that is eating for you with consistency already

2# Take one step at the time in other word switch to mice first than once your BP eats mice with consistency switch to F/T

Right now your priority is to get him to eat so try offering live rats once a week (If your BP refuses wait a week before offering again).

In the mean time only handle him like you have done only when necessary.