[teebob21]

The ball is dead immediately when an obstructed runner is "put out". Other runners must return to the base last touched when the ball is dead.

Why deny R2's attempt to come home? Because by rule the ball is dead. Runners cannot advance during a dead ball except on base awards and home runs (there may be other examples that I have left out).

The mechanics as I would do them:
R1 from 3B is obstructed. PU signals DDB with the left arm + fist extended at shoulder height, fingers forward. (You're probably also holding your mask, so just stick it out there. PU vocalizes "Obstruction" loud enough for nearby participants to hear. I am also OK with a point on this with the right hand. After signalling the DDB, hold it for a couple seconds and drop the DDB signal...we don't need to run around out there like a mannequin.

OBS R1 is played on and put out before scoring. PU signals Dead Ball, and vocalizes "Dead Ball! This runner is obstructed!" Take a short second to scan the field, as you need to know where the other runners are at the time you kill it. During this second or so, make sure play stops. If necessary, repeat the Dead Ball call.

Point at the OBS runner with the right hand, then point at the plate. Vocalize, "The award is home."

Point at R2, wherever she is. Vocalize "That runner: second base." Point to second. Edit to add: If the umpire judges R2 would have safely reached another base absent the obstruction, award that base instead. The mechanic is the same.