Keep the Yorkie. Rehome your Mom.
Hitting a Yorkie is an antiquated, ineffective and unacceptable way to potty train.
I would suggest you do some research and find a positive training technique to housetrain your Yorkie.
Here's one behaviorist's way:
Errorless Housetraining | Dog Star Daily
That's not the only way, so if it overwhelms you, keep searching. The keys are to limit their freedom until they earn it, make it easy for them to succeed by taking them out hourly until they succeed. When they succeed, praise, praise, praise and treat, treat, treat. When they fail, give the dog a firm NO, and calmly take them outside to where you want them to go. Then, roll up a newspaper and smack yourself in the head, because it's your fault, not the Yorkie's.
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Mike ~ Doting Dad to Jillie, Harper, Molly, Cooper, Eddie (RIP), Lucy (RIP), Rusty (RIP) and Jack (RIP).
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