Yes that would be me. Happy to hear you enjoyed it!
I have to think a bit about the first issue you mentioned.
That particular "band" looks funny.
I have a possible solution in my mind, but I'm not really sure and I can't remember the exact name of the setting anymore.
Both would probably only be confusing if I'd try explaining it.
About the second issue though, you could try the following:
1) you could start with setting reflection roughness to 0
2) the aliasing in the reflections could be two things. You can enable soft shadows in the sunlight node or improve the calculations of the reflections (see 3)
3) increase the "ray detail multiplier" inside your render node. This setting changes the detail in the micropolygons that are seen by the reflection rays. The multiplier multiplies the render detail setting from the renderer with the "ray detail multiplier" setting.
So, for example: if you render with detail 0.7 and "ray detail multiplier" @ 0.25 => 0.7 x 0.25 = 0.175.
In other words, the geometry/surface seen in the reflections is based on 4x lower quality than outside of the reflections. Simply put.
Therefore, the max number for the ray detail multiplier is 1.
(double click on the + symbol of the render node, then you should see the "render subdiv settings" node (grey) and inside that node increase the ray detail multiplier from 0.25 to 0.5, for starters)
You may understand now that whenever you render something with reflection that you 1) need sufficient render detail 2) enough ray detail multiplication, to get good results.
