Awww, he is just adorable...and bless your big hearts for saving him from the streets, looking for his owners, and taking him as yours. He sounds like he fits right in.
As for studding, my best advice so that he has the best life is to not do it. Being un-neutered could very well be why he was lost; unaltered male dogs go CRAZY if they smell an in-heat female for miles around and will do anything to get to her, including running away. So, you do risk losing him again. Also, his potty incidents indoors may be because he is marking; neutering *might* help w/ this behavior. So if it were me, I'd neuter...but you have to make the right choice for you. Oh also...prior to breeding any dog, you really should have a Show Breeder evaluate him to see if he really is worthy of breeding/bettering the breed.
And lastly, you have to consider whether you really want to add to the pet population by participating in breeding. Remember, we kill/euthanize 3-4 MILLION PETS every year in the US. So to me, there has to be an
incredibly worthy reason to breed any kiddo in this day and age where we kill so many animals

.
WELCOME to YT - it's great to have you here!