Is there a way to handle focusing when you're filming yourself?
Put a dummy object where you will sit, and focus on that.

With a dedicated video camera, you would normally zoom in on the focus point, set the focus, and then zoom out again for your desired framing. Your camera appears to be a stills camera, and my understanding is that the lenses on a stills camera don't work the same way as the zoom lens on a video camera, so that particular technique might not be applicable (hopefully someone with stills camera experience can jump in here). But definitely set the framing/focus on a dummy object where you will be, and lock that.

If you are going slightly in/out of focus with your movement, you could move the camera further back as well - the further back the camera is from you, the more depth of field (range of focus distance) you will have on the object being focused on. The trade off being that as you move the camera further away, the sharpness of the image may decrease, the more zoom you are using - although you're unlikely to move the camera far enough back in your setup to make a noticeable difference.