Currently the definition of 100% is "Collect all Heart Containers and Cards". Is there a reason this doesn't include broom upgrades? And we could also mention the shoes and the three large keys. Or are those left out of the definition on purpose?

I don't know who wrote the 100% definition list. I define 100% as all cards, all hearts, all keys and all upgrades, which include boots. I saw it as having every slot in the menu filled, all the basic game cards and the unlockable items.

By "all keys", I assume you mean the three large keys, not the small keys in dungeons. Oh, and I forgot to mention the empty box also. That goes in your inventory, so I think it should count for 100% also.

The Steam version of the game comes with an achievement called "100% the game with 37 cards" subtext: "You finished the game with over 37 cards, all the health and broom upgrades!" I think that's the definition that people running 100% on this site are really running against.

Of course, there's the possibility of a run that truly gets everything, including the obnoxiously slow item in the forest. It would not be the first time a speedrun category includes an annoying long wait, but I can see how that wait would make the category unpopular. I think my ideas of getting the shoes, box, and large keys should really belong in the "200%" or whatever category along with all the other post-game stuff. Basically, everything that appears in your pause menu would be in the "200%" or whatever category.

I think that card 49 would probably NOT be included in such a category, because it isn't a real item; it doesn't go in your pause menu. In fact the game's code doesn't even track the item's existence anywhere. All that happens when you open the card 49 chest, is the chest is set to the opened state, and your card count in incremented (and then possibly your save file gets corrupted). The devs didn't put a real item in that chest, so I say the chest doesn't contain an item, and you don't have to get it. At least, if I ever tried to make such a category popular, that would be my argument :)