there a couple mods that claim to do this same thing, but the way that they did it was very basic and is very prone to breaking, which means that the mod doesn't actually work as intended. the way I have managed it is very simple, and yet it's essentially bulletproof.
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the other mods I have tried myself that claim to do this same thing just had the "damage" flag for weapons or armor unchecked inside the fallout 3 GECK, which is very simple but is also time consuming, and it makes it very easy to skip over some items, and the game sometimes just doesn't accept the changes from the GECK in the way that is expected every time, which can cause the mod to just outright stop functioning.
I used the GECK but I used the GECK to get to the base code for the weapons and armor damage percentage, and I changed that which affects ALL weapons and ALL armor, regardless of DLC or Addon.
this type of mod is about as simple as you can get when it comes to installation, either use your preferred mod manager, or if you are hell bent on a manual install, then it is as simple as extracting the file and placing it in your "steamapps/common/Fallout3/data" folder and then make sure it's activated in your mod list