In the card rulings for {Tarmogoyf} It states that it's ability applies in all zones. Would the same apply for {Lord of Extinction}?
And if so, could I use {Lord of Extinction} with {Foul Renewal} to give a creature -1/-1 for each card in all graveyards (Lord of Extinctions toughness)?
Yes and yes. The number of cards in a graveyard can always be determined, so you're good there as well. Note that the use of {foul renewal} will remove him from the graveyard, so you will count one less -1/-1 than before the spell was cast.
208.2a (http://imtgapp.com/forum/index.php?action=imtg;area=rule;number=208.2a): The card may have a characteristic-defining ability that sets its power and/or toughness according to some stated condition. (See rule 604.3.) Such an ability is worded "[This creature's] [power or toughness] is equal to . . ." or "[This creature's] power and toughness are each equal to . . ." This ability functions everywhere, even outside the game. If the ability needs to use a number that can't be determined, including inside a calculation, use 0 instead of that number.
Example: Lost Order of Jarkeld has power and toughness each equal to 1+*. It has the abilities "As Lost Order of Jarkeld enters the battlefield, choose an opponent" and "Lost Order of Jarkeld's power and toughness are each equal to 1 plus the number of creatures the chosen player controls." While Lost Order of Jarkeld isn't on the battlefield, there won't be a chosen player. Its power and toughness will each be equal to 1 plus 0, so it's 1/1.