According to speed equalization page:
"The combat speed of that faster character is assumed to be equalized to the combat speed of the slower character. Every other speed the faster character has is reduced by the same multiplier. This includes the speed of any attacks, projectiles, reactions, perception, flight etc."
That means that the combat speed of Sans is equalized to that of Frieza. Not their movement speed. And since according to you, Sans' combat and reaction speed is much faster than movement speed, he's going to be slower in comparison to Frieza whose combat speed is equal to his travel speed
That means Frieza can easily dodge Sans' attacks (as for Danmaku, Vegeta tried that against Frieza on Namek and it didn't end well. For Vegeta)