[opti]

Sorry I think I’m reading this very late. Hope you managed to improve everything. But if not, here are a few things to take in mind.
The mic is too far away from where your mouth will be. You should place the mic between 3 to 5 inches away from your mouth, depending on the kind of read you are working on.
The box you built might not work as you would want, but I would add a heavy moving blanket and this should cover you too when you are recording.
Hope this helps.