The last one is actually covered by it I'd say, because (as by rules of spell targeting) you cannot see the blood and furthermore (as confirmed by "Water breathing" not working in wine) spells that affect water really only affect water and that’s it. I know you mean it as a joke, but in my experience, punishing a player for trying to find out what you will and won’t allow them to do is a good way to get players that don’t want to be creative. Just tell them that you will not allow it. (Also… poor Mystra for having to waste that much divine power on someone trying to use spells in a way it can’t be used in anyway.) If everyone at your table is habilitated fun, then… well, have fun, but I'd advise against it.

Fey Ancestry just says magic can't put them to sleep. It doesn't cancel all magical effects that include putting them to sleep. But it's more complicated than that. Imprisonment has the phrase "While affected by this spell, the creature doesn't need to breathe, eat, or drink, and it doesn't age." So, if you get rid of the only other effect (sleeping), does that mean they're not affected by the spell, and thus they do need to breathe, eat, etc.? Or does the spell affect them, because it still makes it so they don't need to eat, breathe, etc.? Though you could argue that that's not the only effect of the spell. It also makes it so that you'll be detected by Detect Magic. Being an elf doesn't stop that, so you still won't need to breathe, eat, etc. Unless someone casts Nystul's Magic Aura.