This is just an IDEA, not a tested procedure, but I think it should work:
You need to find the way of repositioning YOR EYES in the same position relative to the camera, so your face will occupy the exactly same spot in the composition, even if the rest of your body, location or background changes. To do this, you need to use 2 position markers that you can easily put in the same position relative to the camera, and then you simply use your eyes to align yourself with the markers. Voila!
Let me attempt to make my idea to be more clear: using scrap cardboard (or similar material) and the hot shoe accessory holder of your camera. The idea is to craft two cards held parallel to each other and attached tho the cameras hotshoe. The cards should be one in front of another from YOUR point of view WHEN you are ready to take the shot. Then you should make a small hole in the card in front an a clear marking in the card on the back (like a haircross or something) Naturally you should see the marking in the second card through the hole in the first one.
As long as your "alignment device" does not get deformed between uses, you can remove it from the camera so you can use it normally for other shots. Every time you need another pic for the project, simply install the cards on the camera and position yourself where you can see the marking through the hole.
You should remember that only one of your eyes should see the marking, so, you must use the same eye to align yourself for ALL the shots. However, if you want to use both eyes, you can either make two markings and one hole, or two holes and one marking (This can be a little complicated and get some trial and error process, or a few math tricks). Using both eyes to align yourself with the camera can get a bit tricky also, because if you align perfectly, you'll see only one marking and one hole... ;)
Using both eyes will also help you with the tilt angle for your face and, depending on the precision or your markings, the distance to camera. But the distance to camera es much simpler to measure with a long ruler or a stick, or a telescopic antenna from an old radio, etc...
I really hope my idea is clear enough to work with. I might elaborate one to be able to show it. I think of a lot of different ways of implementing the concept and or upgrading this one.