Without wanting to sound rude or mean - you've gone way overboard with the bondo. The idea is to work in small batches, rather than slap it all on in one go like it's icing sugar and then sand it off later. It's far less wasteful to work up a smaller batch - aim to be covering the surface area roughly similar to the palm of your hand in one go, if not less than that, and spread the stuff thinly using a good-quality spatula with a clean, straight edge. I've noticed that in some places you've spread the stuff with what appears to be your fingers.
Your helmet isn't beyond salvage, but you're going to need to spend a lot of time, and waste a lot of bondo and effort, on stripping most of that stuff back before you continue. Good luck with your build regardless!