Tony, certainly you can ask questions.

I asked you one and you answered.

Here's another one do you have or can you access a current copy of the NEC?

As far as your original question, yes, you can feed this new panel from a 100 amp breaker and there is no limit for length of a feeder which is what you would have in this case. (not a tap)

Has anyone calculated how this additional load is going to impact the existing service?

Roger