As far as compression goes, what is the likelyhood that the coolant did some major damage to the motor? It was only inside the motor for maybe 3 hours time.

 

None. Water would have no impact on compression, except momentarily while it was water-flooded. After the water was flushed out and burned off compression is normal again.

IT takes several weeks for water to rust the internals, so that's not a concern.

Your engine is fine.