First- WELCOME
Second- i'm willing to bet the issue is due to how VERY early he went home. Yorkies should not go home before 12 weeks- 10 at the earliest. He needed to learn "manners" from his littermates. So now it is up to you to tell him that what he is doing is NOT ok.
I think what is important is that you choose a method and stick with it- bouncing from method to method is goign to confuse him. When Layla was little I decided that what was going to work for us was to flip her on her back (forcing submission) and not letting her go until she was calm and NOT fighting to get away. Here you are mimicking an alpha dog. However, it is essential that you do NOT let him up until he has submitted to you by resisting being on his back- this could be minutes long- but if you were to let him up before this- he wins- and you've accomplished nothing. I also used to stare into Layla's eyes when I did this- to show her I was in control.
Whatever method you choose (i feel the ones that mimic other dogs are the best- ie- the "bite" with your hands on the back of their neck- or flipping them on their back) stick with it.