Update Existing Chrome Extension with 2 Features

I have an existing Chrome extension that automatically BCC's a specific email address for every Compose, Reply and Reply all in Gmail. I have the source code for the extension. I need it updated in two ways: 1. Fix a bug whereby if there is a "+" sign before the "@" sign in the BCC email, the field rejects it 2. Currently, the extension only allows for a one email to be BCC'd in Gmail, regardless of the email account in the drop down (when there are multiple email "from" addresses in Gmail). I need the extension to be able to BCC a different email address for each "from" account address selected in Gmail when composing, replying or reply all. Thank you.