Where is the “Highlight text” icon in Outlook? Why is my font style constantly changing on its own?

I'm a legacy Hotmail user that got switched kicking and screaming to Outlook.  I've since learned to deal with Outlook email rather than change my Hotmail email address. 

1.  I no longer have the highlighter icon in my formatting toolbar and cannot highlight any text in emails.  I also cannot find how to add that icon to the toolbar.  Note that I am a Hotmail user that just got switched to "Outlook" and do not have  or use any Outlook calendaring functions, etc.  I only use it for email and it looks almost like my old Hotmail except for the missing highlight icon and functionality. Thanks.
2. Although I have selected "Arial " as my default email composing font, in just about every email I write, I find Outlook automatically switching me to the Calibri font at a line break or a paragraph break all the time.  It happens just about at least once or twice in any email of more than 10 lines or 2 paragraphs long.  I can't figure out what's causing it since there doesn't seem to be any rhyme or reason - just at line and paragraph breaks.  It is a PAIN to have to keep going in and resetting the font style once or twice per email!'

Thanks for any help or usable answers anyone can supply!