Hi Nathaniel,
I don't think there's much of an issue of sharpeness here. However, focus plus exposure combine Since you are already set up with a trpod and the picture is essentially 3 zones, foreground plus the tree, midground then sky you can improve things perhaps by 3 shots.
I'd then optimize each shot for it's content and select with feather (use same selection or its inverse) for each shot. After that combine the parts each on its own layer. Then add a percentage of each layer to the unchange first layer (the foreground.)
Asher