When the asteroid hit the earth 65 mya did the earth's gravity pull change? By how much? When the asteroid hit the earth 65 million years ago, did the earth's gravity pull change? By how much?
The gravity of Earth did not change substantially.

The strength of gravity on Earth is about 9.8, but varies between 9.76 and 9.83 ms-2(due to Earth not being a perfect sphere)

This can be approximated from the mass of the Earth using $$g=GM_e/r_e^2$$

Where $M_e = 5.97219\times 10^{24}kg$ and $r_e= 6371000m$.

The mass of the asteroid was about $10^{16}kg$ That changes the mass from $5.97219\times 10^{24}$ to $5.97219001\times 10^{24}$. It changes the gravity from 9.8 to 9.800000001

In other words. The change in gravity was utterly insignificant. You probably get a greater change in gravity by walking downstairs.