Remember, EB-1B is sponsored by the petitioner.
Re: 信封的姓名地址: whoever signs the I-140.
In my case, it was signed by the Director of International Office.(I know that some cases were signed by HR.)
Re: cover letter 的姓名地址
In my case, it was written by the Chair, so the cover letter comes from the Chair, not you.
After everything is ready, I sent out the pack by myself.
Good luck!