Best proof I can offer: http://imgur.com/a/q4LY2

That is probably OK.

If you see "(Never) Remember History" then that means that all history and cookie settings are set to the default value (i.e. cookies are enabled).
The "Use custom settings for history" selection allows to see the current history and cookie settings, but selecting this doesn't make any changes to history and cookie settings.
Firefox shows "Use custom settings for history" as an indication that at least one of the history and cookie settings is not the default to make you aware that changes were made.
If all History settings are default then the custom settings are hidden and you see "Firefox will: (Never) Remember History".
"Never Remember History" means that Private Browsing is active and "Always use private browsing mode" gets a check mark.
"Use custom settings for history" stays selected if at least one of the History or Cookie settings is not the default to make you aware that changes from the default setting have been made.

You can see in the screenshot that I DID change a setting. Specifically I changed "Accept third-party cookies" from "Always" to "from visited".

When I restart FF, then select custom settings again, this item will be reset to "always".

Start Firefox in Safe Mode to check if one of the extensions (Firefox/Tools > Add-ons > Extensions) or if hardware acceleration is causing the problem (switch to the DEFAULT theme: Firefox/Tools > Add-ons > Appearance).

• Do NOT click the Reset button on the Safe Mode start window.

• https://support.mozilla.org/kb/Safe+Mode
• https://support.mozilla.org/kb/Troubleshooting+extensions+and+themes

If you do not keep changes after a restart or otherwise have problems with preferences, see:

• http://kb.mozillazine.org/Preferences_not_saved