I actually read the instructions and watched the video!
Not only that, but I even looked through the google sheet.
First, talk about nifty! That's really something. Love the idea, and I see where you're going with it. [Or at least where you've got it figured out.]
Now, to the gritty details. In no particular order:
* I am in Canada (EDT right now), so we should be able to chat, Skype, whatever without too much trouble.
* We can adjust price, milestones, etc. depending on how the details shake out.
* I think in XL, less so in GS (=google sheets); should be able to convert with little effort, but consider this if it could be a show-stopper.
* Please read my reviews concerning XL. I've been away from Freelancer for several years, but the appropriate reviews should still be relevant.
* I used to track my exercise (steps, calories, via a decent pedometer), weight, BMI, food consumption (simplified), with a graphical output (not quite as complex as yours); Over a few years Weight went from 187 to 142, BMI from 30 to 14. Not bad if I say so myself. I have some idea of what you're looking for.
* We will need to talk a _lot_ about how to approach some of this, but it _can_ be done.
* I am still mired in XL 2010, so I cannot guarantee any newer features will work correctly out of the box; you may have to do some extra testing.
* Please tell me more about Loom. [Looks very useful!]
Thanks for taking the time to read my (far too wordy) proposal,
David