Here is the best way to keep your points on. Forget the acetone and swabs to clean the inside of your points, I used to do the same as well as run a tap in the point to rough it up.
Here is the easy way, the never loose another point way. Make a cone of 100 grit sandpaper that fits on the taper of one of you broken shafts. Wrap the paper around the taper and insert it in the point. Twist the shaft and paper around a couple of times until you have bare metal showing inside. You can't get the inside of the point any cleaner than bare metal. Tap the sanding dust out of the point and glue the point on with Defcon 5 minute epoxy from Walmart, fast, cheap and easy.
You can still take the point off with heat, just takes a little more. I have never lost a point since I started using this method and lost 5 or 6 on every 3D round I shot when I used hot melt.