You missed the part where he called shikamaru troublesome with his rinnegan implant and gedo mazou. If you think that Itachi is a threat to obito then you agree that shikamaru is an even bigger threat.
"Regrettable" and "troublesome" are not synonyms. And besides that, in context, Shikamaru is leading a five-nation army against him with dat giant brain. So even if you think he meant Shikamaru was troublesome, I'd ask you if you'd think the same thing if it were truly a one on one situation. I kind of doubt it.
but itachi never made a move on obito?
We don't know that. We do know that Obito could effortlessly teleport away if he did though.
And besides, Itachi calling Obito "pathetic" and Obito calling Itachi "amazing" doesn't paint equality.
When you think about it, Obito didn't even show himself to Akatsuki members until after Itachi died.
Yata blocks physical attcks Kumai isn't physical nuff said.
Nowhere is it said that the Yata Mirror is limited to physical attacks. "Completely invincible" doesn't imply as much.
And the databook straight says, multiple times, that it can plot attacks that aren't physical, too...