RDR2 Story Mode completely broken - no NPC interaction, horse won't respond, can't use weapons, ESC menu broken

I'm playing the Steam version of Red Dead Redemption 2 with no mods installed.

The problem started during a Chapter 6 mission in Annesburg with Dutch and Micah. Since then, my game is completely broken.

Symptoms:

- NPCs don't react or interact at all.

- I can't greet or talk to anyone.

- My horse doesn't respond when I whistle.

- I can't mount the horse.

- I can't draw or use weapons.

- Mission objectives don't progress.

- Lawmen appear transparent.

- Pressing ESC only makes the screen black and white, but no menu (Map, Story, Settings, etc.) appears.

- Some textures load very slowly or don't load correctly.

I've already tried:

- Restarting the game 3 times.

- Restarting my PC 2 times.

- No mods are installed.

- Steam version.

Has anyone experienced this before? Is this a corrupted save, a broken mission script, or damaged game files? Is there any way to fix it without losing my progress?