WELCOME to YT. I'm so sorry for the loss of your Father, but bless your big heart for taking in his little furkid
....I'm sure that meant more to him than you know. Yorkies are big dogs inside small bodies, so I'm not surprised he gets along fine w/ your other doggies. That said, you're very smart to already realize that he shouldn't be left alone w/ the larger ones since they could hurt him, just by playing and through no fault of their own. Glad you found us!