The only thing I have to add - for any "first" stitching of the binding -
ALWAYS stop the seam width distance away from the end.
Many books say "stop 1/4 inch from the corner" - which is fine and dandy if your seam width is 1/4 inch.
I am happy to note that you stated your seam width is 3/8 inch and that you say to stop "just shy" of 3/8 inch.
My finished bindings are close to 1/2 inch wide - so I stop "a hair or so" more than 1/2 inch from the corner.