Marking is a normal thing for a male dog to do no madder what age the dog is. Not even neutering will stop it totally. My quincy was 9 before he was neutered and the only time we have issues with him marking is when one of the girls is in heat.
Was your boy totally potty trained before this started to happen? If so he may just be regressing do to a change taking place in your home.
The humping behavior can be stopped. You just need to correct him before he gets too far into his obsession. Take away any toys that he uses for his hump buddy. Than correct the behavior not the dog if you know what I mean.
When he stops the behavior... reward him with lots and lots of praise. Even if you have to do it a dozen times, until he gets it.
Or ... should I say doesn't " get it " .....
