You did an amazing job! It's simply beautiful, but it's horribly inaccurate.

First of all, Casterly Rock is not a sea-stack. The only castle in westeros built like that is Pyke in the Iron Islands (which is built on top of multiple sea-stacks). The Rock is on the seashore, but it is exactly what it's name says, a massive vertical rock mountain, very much like Gibraltar (in fact, GRRM patterned the Rock after Gibraltar). The castle itself is not really visible for the outside as it is almost entirely built inside the Rock itself. there is an entrance several stories above the surrounding flat lands (the Lion's Mouth), as well as its own protected port, which goes into a cavern between two natural rock jetties on the sea-side. There are some visible battlements on its exterior as well as a small ringfort at the top which acts as a lookout post/and lighthouse. a major part of the reason why the Rock has never fallen to any army is because it is a self supplied mountain with extremely limited entry and exit points. Lastly, The Rock also does not open onto Lannisport like this picture shows, but is rather a somewhat away from it, with a forest in between he two