As you may have already noticed, the FtpResponseStream does not contain the result of PWD, SIZE and MDTM methods. You can get those from the FtpWebResponse properties

1. To get the result of the PWD method (WebRequestMethods.Ftp.PrintWorkingDirectory) check the FtpWebResponse.StatusDescription property
2. To get the result of the SIZE method (WebRequestMethods.Ftp.GetFileSize) check FtpWebResponse.ContentLength property
3. To get the result of the MDTM method (WebRequestMethods.Ftp.GetDateTimestamp) check  the FtpWebResponse.LastModifiedProperty