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I have a bunch of formulas in my inventory, can I sell them and still be able to make the potions? When I try to read them by double-clicking, it just says I can't do it. If I sell them, they still appear in the merchant's inventory, does this means I have yet to learn them? And if not, then why the hell would they still appear, they're useless! The menus are garbage and make my head hurt :(
It seems you have to keep them in the inventory if you want to be able to craft potions - to test this, I sold 2 different formulas to a merchant and tried to mix the respective potions afterwards, but they weren't on the list. I don't know why CDP scraped the system from Witcher 1 which worked perfectly.
They also removed - it looks like - the secondary properties the elements have, so no more paying attention to the mixes to get optimal effects. Too bad, that made it a bit more challenging (and fun, IMO).
One thing that did carry over from the first game is that the alchemy crafting screen does not pick the most optimal ingredients for you.

It should be designed so it will always pick an herb first for all potions, since the only thing you can use herbs for are potions. It's annoying when it auto picks reagents that can be used in other types of crafting when there's a big stack of perfectly good herbs.
the question stands. is the amount of potions in the manual all the potions in the game?

and can i still turn my blood into poison?

also can i poison myself with a bad brew?