What kind of glue are you using? The best way to do the ends and get the excess fabric out of the way is to cut a piece that matches the end and sew the two pieces together. Then you are cutting the sewn in piece and not the larger middle section. Then if you make a mistake you are only replacing the small end section, and not the whole dash.
For the ash tray hole, cut a horizontal line in the middle about 2" long and then four angled cuts up towards each of the four corners. Fold the fabric onto the back side of the dash and glue the vinyl down. Then just put the ash tray back in to hold the vinyl in place.
No one lives forever, the trick is creating something that will.