Love that coat!
Pretty puppy!!
About the excited sit... I'd say you might just have to wait it out - it should calm down as he gets older and calmer. What ever you do, don't add excited energy into the excited sit... kids are good at adding excitement (running, laughing, etc.), so I wouldn't worry about his excitement when they're excited - not sure you'd be able to do anything about it at that point. When the rest of the house is calm, how does he do?
I'd get in a calm place myself, first, have him come to you, then ask for a sit - and freeze... if he moves, just stand there... wait for a split-second of alert attention without the scooting (even if it's just due to confusion over you not moving) - then Release and Praise! Each time, when he finally takes a breath and stops scooting, wait an itty bitty bit longer before you Release and Praise, so he knows it's the sitting still that will get him what he wants (Praise, love and attention!)
We often have to ask for a calm 'sit & wait' outside the door, before Denna is allowed inside... that way she gets in the habit of leaving excitement outside, and being calm inside. When guests are over, it's very hard for her to start out calm... but she gets there. She knows she'll get sent outside if she doesn't calm down (and she's 2, so it's a little easier for her to calm down).
Sounds like he's a real sweetie!!
Thanks for the update!