My concern is that in the OP she states that the extra legs drag- that seems to be an invitation for infection to me, as well as that there is significant care that the owner must perform, and thus the chick must endure, because of the poo getting on the extra legs constantly. That's going to be less of a concern as the poo becomes more cohesive, excluding cecal poos, of course- that will be fun!
I'm thinking of the chick when I suggest it may be best to amputate the unused limbs.
I'm wondering if both vents are functional, whether both oviducts will produce, as well? How very interesting a study it would be, assuming both don't try to produce simultaneously, which could be catastrophic.
Hope your baby is still doing well- can we see some updated pics?
Edited to add: I like the name- my vet has an office cat that has 3 legs named Trivet, and had one years ago named Tripod.