Real life with Siegfried

Real life with Siegfried can be challenging for a permissive "master" who finds him too darn cute. My wife is a much more effective top dog to Siegfried than I am. To him I am more like a pack buddy with whom he plays rough and competitively, jumping up on me, gleefully ambushing me from behind or the side, kissing me with his nose or nipping at me or my T-shirt as he flies by. We'll play like that for a while, until he gets winded, then when I kneel, he'll come over and burrow his head against me for some pats and rubs. It's great.
    But it's always back to the roughhousing. And this sometimes becomes a bit much to take. I've occasionally slapped him, and while that sort of seems to help at the moment, it's of course counterproductive in the long run. But it's amazing how he seems to take the slap in stride, as though it might just be a part of the rough play—for which I'm thankful—while I'm feeling guilty over it.

Now, I'm not blaming him; I'm sure he's just taking me "at my deed," expressed by engaging in competitive play with him ever since it was apparent he incorrigibly wanted to roughhouse. As the one who's supposed to be in charge, I'm to blame. I acknowledge it. Trouble is, it really needs to stop, for my sanity and Siegfried's good too.
    Only question is: How? I sort of need to start over from zero, probably. Do I need to go to another class? Do I need to read a book? I've already read and much enjoyed Karen Pryor's Don't Shoot the Dog, a wonderful book about positive reinforcement training. It's principles seem so clear and workable. But I just don't seem to "have the status" to work with Siegfried as a trainer...or something.
    One thought I've had is to just go back into full-trainer mode, complete with treat bag and go over all of the basic stuff from class. Sit, down, stay, leave it, wait, come, etc. I can't remember the last time I wore a treat bag. I guess I'm derelict in not investing much reliance in that.
    Stay with Siegfried? At this point, stays beyond a few seconds seem absolutely, utterly out of the question and unimaginable. He can hardly stay for five seconds. I realize that this is because we haven't demanded more. We're going to have to work up to longer stays, that's for sure.
    Sofa? Siegfried already thinks he owns our sofa, jumps up there at will, even though we tried (perfunctorily, I admit) to make it a permission-only thing. He's a very assertive guy and so darn cute!
    He's habitually and ever nosing into our pockets when we're sitting down (he could probably be trained to be a very effective pickpocket).
    And, generally, he is ever on the lookout for something to occupy him, very curious (and assertive about it, too), checking out table tops, etc. for something interesting to steal.
    We have a nice, extra-big two-door crate for Siegfried, and he will actually march right into it if we show him a few potato treats and start walking toward it. (This is what Karen Pryor calls a bribe, I guess.) He trots on ahead with his wonderful show-dog gait and goes right in. He will actually "stay" comfortably in his crate for a long time, and only rarely does he object by making a racket. Maybe we can take advantage of this to bridge to stay in the proper sense.

Siegfried is almost a full-time occupation at this point. Fortunately, after he lies down for the night, he's pretty quiet until one of us gets up. Wonderful bladder and bowel control he has. For him to learn to just "turn it off" and stay for a few minutes would be wonderful. He'll often lie and nap for an hour while I'm, for example, sitting at the computer. But at other times, say right before lying down for the night, when I'd like to sit in a chair and quietly read for half an hour, he's pushing at me, nibbling my feet, etc. About all I can do (besides making sure that he doesn't need to go out to poop—seriously nibbling us seems to be his way of communicating that he "needs to go") is to shove or bribe him into his crate. (The only way to "make sure" he doesn't need to poop is to take or let him out and see whether he poops or not!)
    A credible vision of myself as top dog and Siegfried obeying me would, if I could form it, be highly motivating for me to do whatever it takes to realize it.