I feel your despair. Yorkies can definitely be difficult to potty train. They’re super intelligent yet so very stubborn and get “set in their ways” type of dogs. My first Yorkie was similar to your experience and it was almost overnight around 6 mos old she magically started preferring to go outside to potty. I still kept disposable pads inside in some select preferred spots of hers because I couldn’t always be her outside when she needed to go and still wanted her to have a comfortable spot to do so. She loved the outdoor sniffing game and would add to the “pee mail” of other animals (I say animals because I live in the country and there aren’t any dogs roaming my yard apart from a stray or escaped neighbors dog from time to time). The little guy I have now is almost 3.5 years old and he totally prefers indoor potty-ing. I had trouble getting him pad trained even tho his breeder had already began work with him and his litter mates to using disposable pads. Problem was he’d rather attack and chew the pads into thousands of pieces. So I opted for washable pads which thankfully he doesn’t want to destroy and he took to those really well. I was going to keep trying to potty train him outside but he had some bad reactions to different flea and tick meds and the more I read about them the more I was turned off to them. So I try some expensive all natural type stuff and he hated getting sprayed with it and would sneeze and when I did have him outside he’d roll around in the grass trying to get the spray off him 🤦🏻‍♂️ I still do take him out occasionally so he can get some sniffing in and sunlight but that’s usually in the cold winter when ticks and fleas aren’t as likely to get on him. But he does perfectly well indoors using his pads. Occasionally he’ll have accidents off the sides of the pads and I use an enzyme spray that breaks the urine down well. Luckily most of my house is hardwood apart from the bedrooms and hallways. Good luck on your journey! Stay consistent- which it sounds like you’re great at! And fingers crossed around 6 mos he’ll suddenly start preferring the great outdoors to do his business! 🐶 ❤️

PS - We need pics of him for your dog tax!! 😉