2) Not too bad I had a 32 inc make a lib call once.
3) no the using 1 is good. I tells the compiler to switch banks. the question is are an other interupts with a higher priority using that bank too.
4) the proper way to set the I2C clock is to see it high, then read the pin back untill it reads high. this cover clock streching and bus capitance. But is not your problem here.


I assume you tried the code out of the interupt to be sure it works. make sure the interupt is not being interupted by another interupt.