I appreciate your detailing the creative process of your endeavor. For focusing the camera, if you can afford generous light I'll say choose an aperture stop that'll give you a narrower opening for light (say upwards of f/5.6 upto maybe 8). That'll give you a deeper depth of field. That's just jargon to say more area of the image will be in focus. Then you can place something about where your head will be, go behind the camera, focus on that thing using manual focus. You'll be good afterwards. A little trick could be to use auto-focus to focus on that thing you placed, and once the focus is locked, while will depressing the shutter button halfway, with the other hand switch to manual focus. When you're rich and famous from selling your course you can buy a camera with follow focus 😉

The downside of using a narrow aperture is that you're telling the camera lens to let in less of whatever available light. So you need an abundant supply of illumination to compensate for that austerity instruction. So if you can do it outside or on a balcony, it'll be perfect. That's why I started out with the conditional “if you can afford generous light."

Good luck, and I hope the few tips help.

P.S. An easy way to adjust aperture and not mess everything else up is to use the Aperture Priority mode of your camera. I think your model labels it as AV. It's on the dial on top where you have AUTO, M, TV and what not.