Because you painted over the silver paint, there is great chance that the new paint will tear off. You should have sanded the old silver paint, applied primer, applied couple of coats, and then baked it in oven. I admire your work of cutting and spot welding. Doing that, you can creat a "new car" from two, one that is damaged in the front and the second that is damaged in the back. Overall, you seems to be a great techinician, body worker, and painter.