I go mostly by gathered information. As far as you have gone sounds good. The head to tail taper with horn slip reinforcement was a new idea in Tudor, not mediaeval, times. Previously the nock was strengthened by being left the maximum thickness while the shaftment was much thinned to improve archers paradox. With ½” thickness and 1/8”bowstring you wouldn’t need binding reinforcement. There may have also been pieced nocks besides the brass ones from pre-Viking Scandinavia, but I don’t have the info..
Fletching is best when cut and trimmed, but was sometimes stripped as Ascham mentions. Four vane fletch was used on Nydam and some Viking arrows but three vane was more common. Some archers find four vane more accurate, and it fits with cross nocks. I don’t know about the fletching grooves, which were used in crossbow bolts. It sounds like you are thinking of the Roman period Nydam arrows that with shaftment wrappings and birch tar are a real challenge to reproduce. Half inch shaft sounds good . Most mediaeval arrows I know of are tthat maximum thickness. Some fletching lengths; Nydam-3 ¾”, Alemannic-3 ¼”, Viking- 4 !/4..Tudor ones went up to 9”.You are pretty safe with either swine back or square shorn fletching for any mediaeval culture.
cheers,
Erik