Sorry, Roy. I missed those questions. I start self nocks with a single band saw cut then open it with a thin blade and emery cloth folded over and over again to widen the nock. I've seen folks first drill a hole in the shaft which becomes the throat of the nock and widen the gap so the string snaps on the nock similar to your method. I like a loose nock on my arrows and I nock over the nock point so I have to hold an arrow on the bow, across my lap while hunting.
Goob, I have had plastic nocks break but never had a self nock break. I've never really noticed any wear on self nocks, maybe because mine are loose. You can add a hardwood, bone, horn or even rawhide to reinforce the self nocks by inserting the spine in the shaft perpendicular to the nock. With these reinforced self nocks there is no reason to add the sinew wrap.