Here are some common uses of the objective/subjective distinction in ethics:

• Moral facts are objective1 if they are made true or false by mind-independent facts, otherwise they are subjective1.
• Moral facts are objective2 if they are made true or false by facts independent of the opinions of sentient beings, otherwise they are subjective2.
• Moral facts are objective3 if they are made true or false by facts independent of the opinions of humans, otherwise they are subjective3.

Hmm, that doesn't cover the way I understand "objective" and "subjective" - I see them as referring to whether the answer to a question varies from one person to another, i.e. whether they are function of the person speaking. "Is that play interesting?" is subjective4, "Does that play follow the three unities of classical drama?" is objective4 - so to match your pattern it would be something like "Moral facts are objective4 if they are made true or false by facts independent of any single human, otherwise they are subjective4".

i.e. it seems to me that some things are considered "objective" if they are merely social customs that may not hold in another society in another age.

But my thinking around this isn't very clear, I'm mostly reacting to the fact that none of the definitions you listed seemed to fit the way I understood the words.