Some triggered abilities trigger "whenever you sacrifice a Blood token." These abilities trigger regardless of why you sacrificed that Blood token.

You can't sacrifice a Blood token to pay multiple costs.

Some spells that instruct you to create a Blood token require targets. You can't cast these spells without choosing all required targets, and if all of those targets become illegal targets, the spell won't resolve and you won't create any Blood tokens. If some but not all of those targets become illegal, you'll do as much as possible, including creating Blood tokens.

If an effect refers to a Blood token, it means any artifact token with the subtype Blood, even if it has gained other subtypes.