On point settings can be challenging, even when you have done them before. But you have done very well so far in figuring out what sizes to cut. Assuming those are unfinished sizes, so your block size is 6” square finished, you have the theoretically correct size setting triangles cut. And you cut them the correct way—to have the straight grain of the fabric on the outside. So that is all good.
So...what is going wrong? The blocks in the runner may not be coming out at 6.5” unfinished. Did you square them up before you put them together?
Those pesky double diagonal cuts can be harder than they seem. If you measure one of the short sides, it should be a tiny bit over 6 7/8”. The dog ears extend past the edge of the block to which you are attaching the triangle, and your seam, if perfect which mine never are, intersects right at the raw edge.
Mine never do. I just start with slightly bigger triangles, like 10”, slice them twice diagonally, attach them, and trim the edge to make sure there is a 1/4” seam allowance past the points.
The four corner triangles are cut from 5 1/8” triangles sliced once diagonally; I would probably use 5 1/4”. Again, you can always trim later.