For RPM change, you can take the difference between the last
reading and the next. Divide it in half and add it to the current timing.
You will be real close.
It won't misfire but it can detonate or ping as it is called.
You might want to bias it such that if accelerating, You only add
1/4 the difference while decelerating you subtract 3/4.
I do hope you've stopped calculating time to RPM and back to time.
If you plot is out with time, you'll see that the advance curves make
more sense. After some RPM, the advance is almost a constant
time ( burn time before TDC ). Use RPM and degrees only to create the time to time
table.
Dwight