Hi and welcome to D/S,
It sounds like you are seeing things clearly and that will serve you well in the weeks to come.
I too am alone now in a very large house that was purchased (by me!) to house him and his 5 kids. It was already starting to feel "too big" as the kids got older and were around less, but now it feels enormous. There's just me here, with one fat cat and one small fluffy dog. (thank GOD for them, btw. If you don't have a dog, I highly recommend one!) The house is a split level and I'm literally never downstairs unless I'm leaving through the garage or tossing in a load of laundry. Big, empty, echoing rooms down there... its just weird.
At first I was just so MAD and jealous that he was the one who got to leave. A fresh new start, in a new house with a new woman. How bright and shiny AWESOME for him. And I'm stuck here with all the bad memories (ouch), the good memories (double ouch), and the memories of OW being here when we were all friends (don't even get me started....).
Anyway, one thing that has helped me is sort of "reclaiming" the areas of the house I do use. I don't have a lot of money to spend, but I've found that just moving things around helps tremendously. Now things are where *I* put them, not where he left them or even last saw them. It may sound dumb but its really helped me feel more of a fresh start, even in a place that was ground zero for the end of life as I knew it.
The other thing you mentioned was the lack of commotion in the house. I went through that too. The house went from full of love and life, to full of anger and drama, to full of angst and tears, to .... *crickets*. It's definitely very weird. My counselor calls this time "making peace with the peace", and though its harder than it sounds, you will get there. You're already appreciating some of the benefits of living alone, and the luxury of pleasing yourself, instead of walking on eggshells and trying to anticipate what bullshit the WS is going to pull next.
I have enjoyed that optimistic feeling you are talking about, and then also been pulled back into a state of feeling rejected, sad, and utterly ALONE. That change scared me.... but its normal. Just don't panic if one morning you wake up and find your optimism has abandoned you without warning. Keep strong, it will come back.
Big hugs to you through all of it!!