Very difficult to control a mortising bit freehand. You need to use a template. Make the template long enough to clamp firmly to the faceframe below, or above the mortise location. You haven't shown the hinges you're using, but there are offset hinges made just for this purpose. That's a pretty deep mortise for a hinge, which is why I mentioned the offset hinges. I'd check the hinge issue out before cutting anything.
Making a template for me means drawing an outline of the hinge piece onto the template material, then cutting it out with a bandsaw. Then a little sanding to smooth out the edges.
You might have to make an extra thick tempate for this to work right. I have great results from a half inch Yonico bit I use just for this kind of job. If necessary, you may still have to do some chisel work to square up the corners, depending on the hinge shape.
Here's a 3/8ths mortising bit that might work for you. https://www.amazon.com/Yonico-14122q-8-Inch-Diameter-Template/dp/B088GV3W8Q/ref=sr_1_3?crid=3M2304Z7CJJGF&keywords=3/8ths+mortising+bit+for+routing&qid=1664212270&qu=eyJxc2MiOiIxLjg5IiwicXNhIjoiMC4wMCIsInFzcCI6IjAuMDAifQ==&s=hi&sprefix=3/8ths+mortising+bit+for+routing,tools,150&sr=1-3&th=1
Making a template for me means drawing an outline of the hinge piece onto the template material, then cutting it out with a bandsaw. Then a little sanding to smooth out the edges.
You might have to make an extra thick tempate for this to work right. I have great results from a half inch Yonico bit I use just for this kind of job. If necessary, you may still have to do some chisel work to square up the corners, depending on the hinge shape.
Here's a 3/8ths mortising bit that might work for you. https://www.amazon.com/Yonico-14122q-8-Inch-Diameter-Template/dp/B088GV3W8Q/ref=sr_1_3?crid=3M2304Z7CJJGF&keywords=3/8ths+mortising+bit+for+routing&qid=1664212270&qu=eyJxc2MiOiIxLjg5IiwicXNhIjoiMC4wMCIsInFzcCI6IjAuMDAifQ==&s=hi&sprefix=3/8ths+mortising+bit+for+routing,tools,150&sr=1-3&th=1