Hi and welcome to YT, also congratulations on your new baby.
He sounds to be a healthy weight for his age, although he is a little young to be away from his mother (12 weeks).
Because of this you will have to keep a close eye on him, I recommend taking him to a vet for a check over and you also need to watch out for hypoglycemia.
Because he is young you will have to teach him bite inhibition (his mother would have taught him this).. it can be a nightmare at times, I know because my pup was taken young and I am going through this myself but keep at it and they will learn!
Also white on the chest is common in yorkie pups as is white on the toes (my Poppy has white on the chest, toes and chin) this does not mean that they are a parti carrier as like I said it is very common.
Was one of the pups parents a parti?
About the ears, your pup will be teething and this can effect the ears standing. Not all yorkie pups ears stand at the same time, some take longer then others and some dont stand at all... my Poppy is 13 weeks, her ears are still floppy but she is holding them alot higher then before.