Has anyone else had trouble with a boarding dog marking its territory on everything in your house?

I have enjoyed all the dogs I have watched on Rover up until now. I am watching a Maltese/Terrier mix, he is is almost 9 years and has never been neutered. I did a meet and greet with the owners and they insisted that he is fully potty trained and never has accidents in the house. That has not been the case. I'm on day 3 with him and he is trying to mark everything in my house. I have to keep him closed out of all rooms because he can not be trusted. He has peed and marked on a decorative baskets, my white curtains, the corner of my bed/bedding, and my end table. This is all after spending time outside getting all of his bathroom breaks out. I am so stressed out. Rover hasn't been able to offer me any advice, Im counting down the days until this pet goes home because my dry cleaning bill is getting higher by the day. On top of this I can barely let him enjoy walks and the park like I do with my own pets or other dogs because he wants to hump everybody's dog. I feel like I got tricked into watching him. I have to keep him away from my 2 dogs because he will not leave them alone. Its just been a terrible experience.