Thanks for your post, sorry to hear of your troubles.
Please make sure to contact IK Multimedia technical support
here. They can help figure out what is going on and how to help.
In the meantime, please go ahead and try checking your Menu > Settings in AmpliTube. There are some Input/Output level controls here. Set these to "0" to start. An input or output level set too high can result in extra noise.
For issues with clicks/pops distorting your signal, try adjusting your Menu > Settings. Turn Latency to "Low" as opposed to "Ultra Low", then turn Oversampling & Auto-sleep "Off". This should help reduce processing power required for use with AmpliTube. Another way to free up processing power is to close all background apps and a hard reset of the iOS device (Hold the LOCK & HOME buttons on your device until you see the Apple logo).