For the GUI, try this addon:

https://addons.mozilla.org/en-GB/thunderbird/addon/theme-font-size-changer/

For the text size inside messages, there are other settings.

http://xenos-email-notes.simplesite.com/417754775

I am sorry that I have no answer for the missing standard buttons. Mine have never gone and I don't know how to replicate your issue.

Half helpful. I can SEEE the letters .YAY!!! And appreciated. Thank you.

Is there some way to fix the other problem? The -+ x not being in the right hand upper corner? See picture.

Zenos said

For the GUI, try this addon: https://addons.mozilla.org/en-GB/thunderbird/addon/theme-font-size-changer/ For the text size inside messages, there are other settings. http://xenos-email-notes.simplesite.com/417754775 I am sorry that I have no answer for the missing standard buttons. Mine have never gone and I don't know how to replicate your issue.

I finally figured what was causing the - = x to be absent from the top right corner. there is a addon/extension called Classic TB2 1.3. I installed it and that's when the top right hand items disappeared.

Solution: Remove Classic TB2 1.3.0. Use TB Default 45.2.0 - the one what comes withe program.

Again thanks for the help. Theme-font-size-changer lets me SEE the writing!! YAY!!!