I was always told dogs licking faces in handed their ability to smell them. Kinda like when you hug your SO and burry your face in his neck. As far as dex "dominating" could be he was trying to play. Dex is a big boy and a 45lb dog isn't much for playing with the GSDs. I know Sabo and his 8mo pal Berlin play ROUGH. Its hard watching them play because I'm so worried one will accidentally get hurt!
I don't subscribe to that "alpha" crap either. Are there pack leaders sure. Do pack members often do what they want anyway? Yes. I think you did the right thing by leaving- you didn't reinforce the problem and allow it to go on.
I would however, not take the 14yr old and Dex. Dex will do what the 14yr old does and well, he's bigger. A malti rough housing won't be as much force as an 8mo GSD rough housing.
I do highly suggest reading "How to speak dog" amazing book!!!! I am about half way through (have to keep referencing their examples and stuff) and I am really starting to better understand Sabos language and being able to work with him instead of bending him to my rules- I can better understand his actions
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