Alex is a welcoming host and we had no issues communicating and meeting on the first day (even though we were early). We loved Alex's dog too. Clean place.
The cave house is well equipped, but it is more a studio than a house and it wasn't well ventilated. Not for the claustrophobic... I found the bed was a bit smaĺl and umcomfortable for two (I'm 6' 180 pounds). Nice porch area but no view from there.
Location is good but rent a car to start if you plan to use one as it costs 35 euros to get to Finikia by taxi and you can drop the car off at the port when you go.
It might be 10-15 walk to Oia, but be sure to budget at least 35 minutes to walk to see the sunset as it is at the far end.