I am harsh and opinionated? Perhaps we live in different cultures. Who has no intention of following what everybody I know would suggest? I actually have my foot in 2 dog cultures, the service dog world where I have learned much of what I know, and the internet QUE sites and dog forums. Everybody in both areas are very concerned about the poorly bred dogs being slaughtered for lack of homes. Frankly too many of the health and behavior problems plaguing the dog world are in large part cause by people breeding litter after litter chasing the ideal look without regard to the general quality of the dog. Many breeds have been so improved it is difficult to find a healthy, well behaved specimen.
Although neutering often makes a big difference in behavior problems it is no cure all. It is difficult to say whether any behavior problem has a genetic link or is an early socialization and training problem. And we can't neuter all males at 6 months. One important thing in controlling behavior problems of both neutered and unneutered males is giving them proper leadership. Dogs see all the people and dogs in the household as a pack with each having their own rank in the pack and a top dog. Life is much easier if the 2 legged pack members outrank the 4 legged ones. You can learn to play the role of top dog by reading some books or going to a good obedience class. A good obedience class or book is about you being top dog, not about rewarding standard commands with a treat. Start at
http://www.dogsbestfriend.com/ For more on being top dog, see
http://www.dogbreedinfo.com./topdogrules.htm
Specific to marking is to crate the dog when you can't watch it. Otherwise keep a close eye on it. Close doors, use gates, whatever to keep the dog where you can see it. Some people even leash the dog to them. I have a short length of chain fastened to my one computer desk. Any punishment unless you catch him in the act is useless and confusing to the dog. When you do catch him, you can use the traditional ''Bad dog!'' in a stern, but not loud voice, or the more current trend of ''Ut, ut, ut! In a sharp voice followed by taking the dog out. Nobody that knows much about dogs ever hits one.
None of the above is novel. I have seen it all countless times and places. Anybody interested enough in dogs to consider breeding should have done enough to educate themselves to already know it.
Just why should I give my time to help somebody I feel is adding to the problems of the dog world by insisting on breeding an unsuitable dog because of its looks? The one forum I am active on, the administrator would have locked the thread as soon as he saw your original post. By the way, you got expert advice. Neuter him.