Oh the puppy stage, gotta love it. I am by no means an expert in raising puppies/dogs, but here is what I think. (I know, I know, you didn't ask for my opinion, right?

) I think the stuff you described above is more related to MM being a 3 month old (or thereabouts) puppy. It sounds like he is starting to test the boundaries of what he can get away with. He is also trying to figure out his place in the 'pack'. I don't think it is aggression per se, but I agree with you when you say you need to deal with it now because it can turn into aggression if left unchecked. We played really short games of tug (60-90 seconds) with Buffy when she was a pup and she is not aggressive at all. As soon as she started showing any sign other than playfulness we stopped. "Wrestling/rough-housing" was the same, any sign of it being more than play meant it stopped.
As for him getting into stuff he shouldn't, I would use redirection rather than picking him up or having him turn it into a game of chase (puppies love chase!). I also remember our trainer telling us not to hold their muzzle closed as it makes them struggle more. Does MM have a favourite toy? Favourite treat? Get his attention, show him the toy or treat and have him come to you to get it. Another way to deal with it is the bitter apple spray. If it is something he always goes after, say like shoes, spray them with the bitter apple. He will soon learn that they taste bad and will leave them alone. If it is different things he goes after, then you have to try to spray a little in his mouth while he has the item in his mouth. I am so glad my DH never video taped me walking backwards to Buffy and then spinning around to spray her when she had something she wasn't supposed to!

It must have been quite comical to watch!
I also agree with you in having a family meeting to discuss Max and make sure everyone deals with him in the same manner. Consistency in the application of the rules, discipline and rewards is huge. MM will learn that he is on the lowest rung of the ladder and must listen to everyone. To me, it sounds like you know what you have to do to make MM into a well behaved, well adjusted and well loved dog and are doing it. Raising a puppy is very similar to raising children and you have two awesome girls

so I don't think you will do wrong by Max either.
Poor Rufus! I just don't understand why people abuse animals.

And for someone to have shot him!

I am so glad that you guys brought him into your lives and showed him love. From the pictures you have posted, you can certainly see that he understood it and gave it back.
It might just be me, but I don't find puppy talk to be boring. As you said, you are just trying to sort it out. And I think there are several people here who can tell you about their experiences and help out a bit. Every piece of knowledge you gain helps. At least, that is how I see it and I know I have learned so much from reading about the experiences of others on these boards.