The angle block are meant to be stacked to form a vertically straight corner. They willl work but will not be "round'. Half block are square ended & much more difficult to cut if it's desired to reduce joint size as well as there'll be less overlap of blocks but would be "rounder" than full block.
I'd take down 4 ' of the existing wall & go with a bigger radius. Filling the cells with grout/rebar will help with freezing/pushing concern but good drainage behind the wall is even better. The existing wall seems to have held up ok. My first post assumed 8" block but the wall looks to by 10" or 12"??? MikeD74t