"CModelLoader::Map_IsValid" error; Cause known but unsure how to fix

**EDIT: **Fixed by simply using Source SDK 2013 and setting the mod up properly.

Before anyone goes ahead and tells me to look at another topic for help: I already have. Every single one I could find. No solutions helped me.

I’ve recently decided to get my hands dirty and start modding. I’ve been mapping for various source games for a several months and thought it high time to advance a level.

However (as is always my case), I’ve run into an error.
The “CModelLoader::Map_IsValid” error to be precise.
I know the exact cause of it after having fiddled with my compiled .bsp file, but have no idea how to fix it.
What I have discovered, is that after compiling the map through Hammer, and having it launch the game, it will launch hl2.exe that, from what I can tell, only reads the files in half-life 2/hl2 and not my mods’ folder.

Is there any way to fix this? I’m unsure how to launch the mod itself and not HL2.

(The map itself works perfectly, as I tested it by copying it into hl2/maps.)

I’ve also tried running run_mod.bat in my mods’ source code folder, though that also gives me the following error:
“Can’t find background image ‘materials/console/ep2_background01_widescreen.vtf’”.
I can only assume that the mod isn’t mounting the games properly, and thus doesn’t know where to find HL2 and the episodic content.