Hi,
Your disappointment is understandable, given the investment you made. To answer your question, the problem is RAM. The iPod 4 while similar to the iPhone 4
has too little System Memory (256MB) RAM. iOS 7 requires 512 MB.
I'm going to direct your question to some of our 'Jailbreak' experts, to see if that's an option for you.
AA
Sent from my iPad using iPF