This is completely unrelated to the story, but my inner cat-nerd wants to ramble about this for a while. In cats, fur colour is carried on the X chromosome. For the signature tri-coloured coat of a calico, there would need to be two X chromosomes with different dominant fur colours, which would cause co-dominance and, subsequently, a calico coat. Since males only have one X chromosome, it's most likely impossible for an XY male cat to be calico.

Male calicos are very rare (1 in 3000 calico cats born are male) and probably have an extra X chromosome - so Miffy would likely be XXY rather than XY. This chromosomal disorder also occurs in humans and is referred to as Klinefelter syndrome. Due to this disorder, male calicos are most often sterile, however 1 in 1000 male calicos are not sterile. The fact that Miffy managed to impregnate the female cat means that he is a rarity. (Well, there's also the fact that he's some kind of sadistic immortal demon-cat, which means he's even more rare.)

Y'know what, I'd take him if it weren't for my other two cats who I'd be worried about being... well... eaten by Miffy.

Probably should get the female out of there. Take her to the vet, get her spayed, and you won't have to worry about kittens anymore, if she hasn't given birth to then yet. (Hell, get Miffy neutered while you're at it. Taking him to the vet might be too dangerous, just take scissors and snip 'em off - he survived bullets and getting run over by a car, he'll be fine. If you want to be safe, boil his sack in holy water, cremate it, and bury it at a church.) Take the female to a shelter or something so Miffy doesn't do anything. Good luck, dude.

EDIT: The blanket kneading behaviour that was mentioned raises more questions. Kneading in adult cats often comes from from suckling their mother as a kitten. Most cats outgrow this behaviour, and blanket kneading in adulthood can be linked to a cat being separated from their mother too early, which makes me wonder about what Miffy was like as a kitten (if he's even a cat and not some kind of weird demon-thing in the form of a cat). Kneading can also be a cat's way of scent marking - cats have scent glands on their paws, and by kneading a blanket or another soft surface, a cat can mark it as their territory. Kneading is also a self-soothing/comforting action for many cats, and it's considered a sign of trust if a cat kneads on your blanket, and it's often accompanied by purring - which is associated with comfort and pleasure, and the frequency of cat purring has been proven to have both mental and physical health benefits. My kitty, Nico, kneads on my blanket a lot, and he is the sweetest cat I've ever met, so the fact that Miffy does it makes me really wonder about him. It's a gesture of comfort and trust, which doesn't really fit with his violent tendencies. After thinking about this for a while, I'm quite curious and I really want to take him - but, again, I'm worried about my own cats. Miffy definitely wasn't socialised properly, and I prefer my cats uneaten and alive.