In handling him afterwards I gave a more thorough inspection, now that I wasn't worried about making him uncomfortable. I found our cause of death, and it's both heartrendingly sad, and mindbogglingly odd.
Our dear Basil had deformed legs and a nub tail, that much we already knew. But upon closer inspection after he passed, it became apparent that those were not his only malformations. Basil had a mouth, a tongue, a full palate, but at the back, his tongue was attached to the back of his throat, completely closing it off. This kitten couldn't have eaten anything because his mouth was not attached to his throat. He had been breathing through his nose. Our poor Basil never stood a chance. Bottle feeding would have been no help as his mouth was separate from the rest of his body. Surgery was never an option on such a tiny being. I once asked about euthanizing extremely small or young animals who were damaged beyond repair (remember I used to do rescue) and was told by a vet that they could not and would not euthanize because their smallest needle was far too large. We really had no options with Basil, and despite it all, he was a trooper right up to the end. This morning he was still cuddling up with his sisters, still attempting to nurse.
Tonight my heart is broken for Basil, but I take comfort in knowing that we loved him mightily, and we did absolutely everything we could - there's nothing else we could have done, and nothing would have saved him regardless.
I continue to work on #5's bag. I made the straps today but have not finished attaching them to the bag yet. I'm really hoping to have them done tomorrow. It looks pretty nice.