It takes a huge amount of torque to power a 2" diameter face mill through metal. You can use a 2" diameter fly cutter because there's only a small contact area at any one time. But a face mill is different. Even full-size mills have to take light cuts with those things. And if you look at one, you'll notice it has a shaft that's thicker than 3/8". There's a reason for that.
If you want to make a face mill for the Taig, try making one that's about 3/4" across the face. It still may not work, but at least there's a chance...