I totally understand what you are going through. My former puppies did their business indoors and it was very tedious to have to clean the house daily. Imagine doing this for almost 13 years.
This time, my new pack I got them used to as a little girl to go out as soon as they ate. This was so that they would associate that after eating, you have to pee. And well, it helps a lot that I have a garden for them to go out comfortably but in your case, I suggest that you get him used to go out at a certain time of the day or twice a day so that he associates that with doing his business.
I loved your photos and your little dog stole my heart. Cheers! 💕
RE: Oh My Dog! - Peeing Outside, and other less obvious habits