Mark,
In your second situation, I wouldn't ask my partner, nor would I make up some reason to stop play. If coach asks about it, admit you screwed up and move on.
From a partner standpoint, I have had situations similar to your where I could see that a travel that was called, should not have been. i.e., player goes up for shot, get the ball knocked loose, then comes back down to ground with it. parnter calls travel. Oh well I say.
I had a bad experience once with overruling a call made by my partner. And he was a friend!
I was lead, he, trail. As A1 drives to basket, he gets the ball knocked loose by B1.(very slightly I might add, but enough for A1 to lose control momentarily)
My partner, from trail, (looking through backs I might add)
calls a travel. I give the old double tweet and call partner over. I tell him what I saw, (remember I'm lead and play unfolded right in front of me) he says,"no we're still going with the travel." As he starts down the floor, I guess I snapped. I hit my whistle, said very loudly "THE BALL WAS LOOSE, THERE IS NO TRAVEL, WHITE BALL!!!!"
This was the first of a two game set, and my partner didn't say word one to me for the rest of the night!
So when it comes to overruling a partner, I would hesitate to do so, unless the game situation (time and score) dictated that a team was going to be put at a serious disadvantage if the call stands.
Just my two cents worth.