Need help with Garry's Mod shadow settings

So I'm trying to get dynamic shadows working in GMod which requires the shadow setting to be set to high, but for some reason, there are only options for low and medium. I'm using a Nvidia GT630M and apparently the issue is due to the way the Source engine works with Nvidia Optimus or something, but I need a way to fix this.

I've tried using the launch options "-dxlevel 90", "-dxlevel 95" and "-dxlevel 110" (not together of course), but according to GMod, the "Software Direct X level" is still 9.0 despite displaying the actual Direct X level as whatever I set it to. Any idea what I could do to fix this?

I've been scouring the internet for fixes for about an hour now and I'm pretty pissed about this whole fiasco of being unable to set my settings to whatever I want. Alternatively, if there was a way to get dynamic shadows to work without messing around with the shadow settings, that would work for me too. Any help is appreciated.