Ok. First, painting is my business. So, here goes.
The reason for the cracking is this. you are 'piling' on the clearcoat too much. You have to spray on a light coat, allow it time to flash (dry properly) and then spray on another light coat. You can continue to do this but you must give it the time for the solvent to escape before you go to the next step.
Now, for your chemistry lesson for the day. All paint is actually a chemical process. So, when you paint something, you have to give the chemical process enough time to finish its process. If you rush it, the top layer of the paint will crust over and not allow the chemical process to finish. It will cause solvent popping, cracking and other malfunctions. You also do not need to 'force dry' any of these products as it will cause the blistering to be worse.
Fire away with questions. I will be glad to tell you how to fix it.