"But if I thought the runner would have only made 3B without the obstruction, I would award 3B."
OK - I think we're past step 1 on the 12 step plan to recovery.
Your comments above (the ones I and others disagreed with), including your comment at the beginning of the previous post, lead us to believe that you would not award a runner a base (3rd in this case) unless she was either Put Out somewhere, or attempted to make it to said base. But now, you contradict your previous comments, and rule correctly, and in the manner the rest of us would rule.
So what makes this sitch different? The only rule you have to substantiate putting the runner on third in this sitch IS the OBS rule (the USC rule doesn't allow the placement of runners).
Now, step 2 - change my situation to an unintentional act, that causes exactly the same thing. F3, watching the ball head into right starts backing up so that she can back up the catcher if a play develops at home. BR, watching the ball or the coach doesn't see her. F3 crosses into her path before first base, and they crash big. They tangle, take a minute or so to untangle, perhaps BR is even a little hurt. BR stumbles into first base and seeing the ball recovered in the outfield does not attempt second base.
By the OBS rule, your ruling here should be IDENTICAL (minus the ejection, I suppose). Is it? If not, why. If so - what makes you abandon your previous statements in this particular case?