I think this still has a chance, wait on it, eather way your roottock is so small now if it fails it will prolly sprout from the roots. Just put somethink to protect it , like chicken wire mesh or smt.
When i graft, yet not persimmons i awlays use a scion with two buds, u can probably do more on a healthy strong rootstock, but usually 2 buds on the scion is sufficient.