One drought tolerant plant with tons of varieties is sedum. It can be had in various heights and bloom times and colors. I'm not a fan of the commonly found Autumn Joy, think it's overrated, but a good nursery will have a number of different ones to choose from. They require very little care and can be used in pots or in the ground. Just one suggestion. I'm sure more will be along. Sandy

This is very common, especially if around the drain hole. If they are - they are actually fine cracks vs. scratches. I would call a cultured marble supplier/fabricator in your area to see if they have a remedy for fixing them. Unfortunately when they go untouched they really seem to grab everything and discolor in that area. As far as I know, there aren't a whole lot of fixes. I know if there is a scratch on the top flat surface they can often times buff them out, but that might be challenging around the drain hole.

That’s going to be an issue for matching depth to the rest of the finishes as they are very thick. The pool would need to have been designed with a deeper recess around the waterline to accept that depth from the beginning. If the pool already exists, pick something else. Something that won’t rip off your skin by brushing up against it.

The roof to the right of the main house looks like a barn. I'd change that to make it look like the main house. The gable addition you have suggested for the front makes things worse. If adding a detached garage, I would keep the roofs the same. The more elements you add that are different, imo make things worse. When I look at the house, my initial reaction is of the far right side. It just looks off.