Fielder Interference on return to base
 

Man between 3rd and home (doesnt really matter where) caught in a rundown, on his way BACK to 3rd, F5 blocks his path by standing in the baseline (without the ball) making the runner alter his slide back into 3rd. I believe this is clearly interference on F5, does the runner get home, or does he get automatic safe back to 3rd, since that is the base he was attempting to return to? Or, since technically the runner has already occupied 3rd base, he gets "1 base awarded" so 3+1 = Home?

Home.

And it's officially obstruction.

When obstruction occurs, the umpire shall call or signal
“Obstruction.”
(1) If a play is being made on the obstructed runner, or if the
batter-runner is obstructed before he touches first base,
the ball is dead and all runners shall advance, without liability
to be put out, to the bases they would have reached,
in the umpire’s judgment, if there had been no obstruction.
The obstructed runner shall be awarded at least one
base beyond the base he had last legally touched before
the obstruction. Any preceding runners, forced to
advance by the award of bases as the penalty for obstruction,
shall advance without liability to be put out.