Who has experience with vulcanizing tires? How safe are they?

Who of you has experience with vulcanised tires? I saw yesterday morning that I have a screw in the tire, after my steering wheel on the federal road was a bit restless. At the destination after about 12km I saw the air loss, off to the tank and pressed after. I drove this track with about 1,3bar before. The tire man said only from 0.5bar it becomes dangerous for the tire, but which is probably io and also repairable, because it was only a very short scrube, the qu Asi only got through so far that just so air could escape. From inside actually not to recognize the place. Now the tire was vulcanized, but a little murky is already to me, although I was assured that this is as firm as before! Has there already had jmd experiences with it? When I looked at the tire flank yesterday evening, I saw about a length of about 5cm so a “hair crack”, now I know if this was already there before or from the walk The tire is DOT06 and still has a good 5mm. Photo is still coming. The rubber man said the tire is completely io, one would recognize the damage by tissue scraps inside or something. edit: it is a pirelli pzero nero in 195/45/16 77V There are also the spirits, whether one can vulcanize V tires. The first rubber man we can not say because of adhesion etc, two others said this is not a test at all. The little screw was right in the middle in one of the two rain grooves.