That's a beautiful starting post and if I was ready, I'd join you myself. I'm planning to start in March and am preparing myself now.
You might be onto a winner with your mindset as you're prepared for a 40 day rough ride and granted many people do have that experience. But others have periods of difficulty interspersed with relatively mild days where the hardest challenge is getting through the boredom. After the first week, you should have lost all desire to eat although you may still be obsessed with the idea of food, if that makes sense.
It's great that you've recognised the necessity of abstaining from modifications but have somehow missed the implications of using toothpaste and mouthwash. Please let me point out that the mishmash of chemicals in both products will be detrimental both topically and internally as they can and will be absorbed directly through the mucous membranes. Bad breath and a coated tongue are an inescapable part of fasting and should be embraced (from a distance, of course :-))
You've not mentioned how you're working your routine commitments around the fast. Do you have 40 days plus time off or will you be trying to work through it? Do you know the importance of bedrest during the fast to enable the body to efficiently use the reserve energy supply?
I hope that your experience is both fruitful and bearable and look forward to following your progress.