How do I hack the amount of kills, items, and room code just to get to the Sans fight?

If you just want to practice, beat, or just experience the fight without playing the game, there are solutions other than editing your save file. You can find a recreation of the fight here and play it at your leisure. There are also several videos depicting the fight on YouTube.

The actual process of getting a save file is very complicated because of the various checks to make sure the game data is logically consistent, so it's honestly not worth it. Playing the game and grinding through fights is so simple during a genocide run that it would take less time to get to the fight properly than to learn how to edit the files without corrupting anything.

All I had to do was dig deeper into the files on my "cracked" version and found a set of saves...

• After Genocide Final Boss
• After Pacifist
• Before Genocide Final Boss

I copied my saved game to this folder and replaced the files with the "Before final boss genocide" and I got to Sans. With a burnt pan. And all healing items.