Rearrange/Add/Delete Columns In Mail

Since my MacBook Pro updated to Catalina in November 2019, my Mail went a bit wonky. Among other things, I'm unable to:

(1) Rearrange the columns - i.e. From, To, Subject, Date etc.

(2) Adjust the width of the columns

(3) Change fonts of Message List, Message, Fixed-width font

In addition, some messages display a small "to" icon in front of the Subject line, which makes no sense but cannot be edited. Attached is a screenshot.

Thanks in advance for any assistance, it is appreciated.