Covering the crib with a Tallis is not a good idea, the baby might grab the strings and choke. I dont care who came up with it, it is still not a good idea. This is being a chassid Choteh
I am guessing a wet nurse comes from the olden days before baby formula when if the mother couldnt lactate, they needed someone else to feed the baby. Again this is a silly chumra because if the baby needs mothers milk for health reasons (Some Babies cannot take baby formula) its being a chassid Shoteh over the health of the baby