So how big is the gap in most programs?

It is huge.

How many 4kb pages are being used in the above process?

14 MB / 4 Kb = 14 * 2^20 / 4 * 2^10 = 3.5 * 2 ^10 (approx 4*2^10 = 4MB)

What does that say about most of the 2²⁰ page table entries for this process?

They will be empty.