Six months is about average for Yorkies, and with him only making a couple of mistakes a week, I'd say it's pretty darn good. They usually have a setback when they are neutered, but over the next few months start really doing well. The main thing is don't overreact when he makes a mistake, try to ignore the bad, and praise the good. Buy some Natures Miracle and just spray the spots throughly, and blot, so he won't be tempted to go to the old spot. Remember, if any urine is left in the carpet, they can smell it and are programmed to return to that spot, they can't help it, they have to do this, that's why it's so easy to pee pad train them. In a year, you will have forgotten all about this, and be thinking about getting a puppy.
If he hasn't been nuetered, soon he will start marking, especially since you have another male dog, it how they show their dominance, it's not the same as peeing, and has nothing to do with them needing to go to the bathroom, they are marking their spot, or territory.