The Historic District

4"PVC drain pipe is what you want. Your big box hardware stores will have it in the plumbing section.

At 4 mil, they could have used real stone.

Masonry sand is clean fine sand.

As for the type of mortar, the ratio of sand to lime to cement seems to be one of those things every professional has a different formula. Some say omit the lime altogether. The only thing everyone (incl. me) agrees is that the mortar should be weaker than the material around it. How to get that is...

Go the deck screw route. Make sure the screw that you use is rated for PT lumber, or use stainless fasteners.

Its a cultivator. I have a smaller version as yard art in my garden

Congrats on the home. Very nice.

Happy Thanksgiving.

Yes, its common to pitch the surface to direct water away from a structure.

Sorry for your loss.