Can try this, know idea if it is in there. but since it changes fonts : https://addons.mozilla.org/en-US/firefox/addon/theme-font-size-changer/ can also search from the Bar in the URL as there are others. For soft key board, not sure but can try this : https://support.mozilla.org/en-US/kb/accessibility-features-firefox-make-firefox-and-we Note there are issues with this such as high use of ram, heat, and other things. Please let us know if this solved your issue or if need further assistance.

You can look at this extension. *https://addons.mozilla.org/en-US/firefox/addon/abctajpu/