Thank you very much for your kind comment! I’m glad you like the Supply Heart!
And if you want to go with a number for how many SUPPLY per LOOT SLOT, I’d say go with a number that you can fiddle with like 2. Some food that the characters could gather could be worth 3 while other SUPPLY could be inferior or just not that nourishing, diminishing its value to 1. Just add a quality prefix to the SUPPLY! What do you think? 
Late to the game here—on purpose—but while I technically track SUPPLY in game most of the time, I have implemented some house rules to ease the burden of doing so; I take some cues from the book and then just use (what I consider to be) common sense for the rest to create what I consider to be a very workable, playable system to govern this aspect of the game…
The Adventurer’s Pack (ME, p. 44) contains “A torch, bedroll, scrap of jerky, apple, pipe, and rope. This rucksack has been through so much, you’re not sure what’s inside.” I consider this to be the medieval fantasty equivalent of a modern “72-hour kit” that takes up one CARRIED inventory slot, so I rewrote it so that it contains the following items:
Because these represent compact, efficient “hard rations” and other consumables carried together in one inventory slot, I rule that only one Adventurer’s Pack can be carried per character, and it takes up a good chunk of one’s standard travel backpack or haversack (to which some items can be lashed). In a game where a bastard sword or a hoplon rakes up the same amount of “space” as a magic wand or ring—even though I’m not generally one to handwave—I’m perfectly OK with both the granularity and the limitations I have in place. I consider the original Supplies Pack from the Core 2E book (p. 26) to be functionally equivalent to the ME Adventurer’s Pack.
I consider, when traveling through typical unstressed environments, that any character who carries and has continual access to an Adventurer’s Pack will have “enough” food and other supplies for three (3) full days.
If a party is delving into dungeons with complete darkness, I start looking at the torch situation after a day or two, but for 75% of travel through less-than-extreme biomes, this means that as long as the party doesn’t get robbed, they don’t have to worry about fire or food, which streamlines play. If traveling under harsher conditions, I consider the Adventurer’s Pack equal to 3 SUPPLY for purposes of bookkeeping.
If characters want to carry extra food and fire, I consider additional 3-SUPPLY packs of hard rations, 1-SUPPLY portions of tastier foods (like fresh meat, eggs, and bread) to be consumed earlier in the journey, and bundles of 10 torches all take up one CARRIED slot each. (This lets a lone traveler loaded down have a chance to survive a for a week crossing the deep desert. Sure, there are edge cases that could push this rule, but so far I’ve never seen it abused in actual play at my table.)
The PCs can always pad out their safety margin under normal travel conditions by hunting large or small game (where wildlife is plentiful) while on the move (which lets you throw a few extra dice during overland travel) or crafting some torches when they make camp each night (where branches and pitch (or equivalent) can be sourced).
Some of the other “kits” and “packs” described in the starting loot lists in the books get pressed into service all the time at my table. The Trapper’s Kit has a compact shelter (perhaps nothing more than a waxed canvas to make a lean-to or A-frame), but it also contains snares and tackle, so players have made use of the brass wire, line, and small hooks to craft or mend all sorts of useful gear while adventuring. Lamp oil, iron spikes, and other goodies have myriad uses, and I love seeing my players come up with something new in a pinch. It’s a good place to consider implementing the Rule of Cool…
Currently, my party is adventuring on their fifth day in the Underdark. They loaded down with plenty of extra torches, lanterns, and oil along with some extra food before they left the dwarven stronghold, but they have discovered first-hand—especially after two dwarven companions carrying backpacks full of torches fell to their deaths—that resources are scarce in the Underdark. Unwilling to eat the flesh of the sentient foes they have battled and vanquished (many of whom desired to eat the party!), the party is governing its remaining supplies with strict rationing, knowing that a full two days of travel are still expected. They have been very resourceful about looting the dungeon for anything burnable to make fire at “night” when they camp, stealing every scrap of wood, cloth, and leather from a large horde of defeated skeleton warriors to cook their evening bacon and keep watch during a long rest…
My $0.02…