Nice song, nice sound. Now I've got it stuck in my head!
Your voice seems to be coming along. You could brighten the tone a bit. The support sounds pretty good.
Pitch is spot on.
You are correct that we treat the OH vowel as an Open Throat AH with the lips slightly rounded. We want to be careful, though, because if we protrude our lips that will color the sound and make it darker. Since my suggestion is to brighten the tone, we need to be mindful of the darkening factors. Opera singers often want to darken or cover the sound, but for a more modern or rock sound we lean the other way to the bright pinging sound. You are also correct to be smiling into the sound. Imagine keeping that smile nice and bright and just giving a hint of an Oh to the lips, kind of a grinning OH.
Oh, Yeah, and OH, What an OH she Oh's!
She's making a lop-sided Heart-shaped OH with Tons of Teeth, Lifted Cheeks, and a Static Jaw.
Not to mention, she's dressed to KILL in this clip! Oh, what an OH! Hear the AH in that OH? I do!
Yeah, I'm going... That guy looks almost Just Like Pete Townsend!