Between levelling heroes, crafting, raids and troops, I rarely have “enough” food - but knowing that you’re original estimate (only 5.5 million?) was too low makes my head hurt. 
So, just to be clear, you’re talking approximately 18 million food to max a new 5* hero - is this correct? If so, that’s an incredible amount of food, certainly much higher than it feels.
I never counted, so it didn’t seem that high, but I do have all of my farms at L20, so perhaps I am producing more food than I originally thought.
In any case, before I posted the “Speed Levelling” guide, I created a rough-draft thread for feedback and discussion in which @kerridoc brought up a few of the finer points that 7DD uses in the late game for “power-levelling” a new HoTM or Event Hero:
As you might have noticed, his points tie in quite nicely with the approach you are taking with Joon.
In the later stages of the game, efficiency will be more important than speed, and it seems that we are outlining the “fastest” way to efficiently level a new hero here, so I would love to see the spreadsheet when it’s ready!
Overall, while I believe there is a degree of overlap with the “speed levelling” approach, it is probably worth having a second guide that is more appropriate for someone in the later stages of their development, as the “speed levelling” is really targeted at players who have no 4* or 5* heroes, are in a later “early-game” phase and want to quickly field a new 4 or 5* hero.
I am looking forward to your continued contributions and the possibility of working together on a new “power levelling” guide. 
Thanks again,
Tima