Is this sentence in the PRESENT tense or the PAST tense? Without separate lessons in verb declensions it is difficult to know from the construction which applies. If it is an historic statement then the correct translation has to be that the lion ATE the steak. If that is the case, then to mark that translation as incorrect is in itself incorrect. Still, there appears to be little if any hope of D/L taking any notice of this comment, but maybe someone else can elucidate me.
It'd have to be "Il tuo leone". Despite its appearance, "leone" is masculine singular (hence the article "il") so you'll have to use the masculine singular possessive as well. "Tue" is feminine plural (le tue farfalle - your butterflies). Remember that in Italian (and others, like French) the possessive matches with the "owned" object, not the "owner"; "il tuo leone" could mean his or her lion, we don't know without context.
3000, that's not correct. "Eats" as a noun is very colloquial, slang in fact, at least in the US. No educated person would use it that way. "Eats" as a present tense form of the verb is absolutely correct. Example: "She eats dinner at 9 every night." In this example you could not use the present progressive tense as you suggest: "She is eating dinner at 9 every night" would be absolutely incorrect. "Ate" is obviously a correct past tense form, as is 'was eating', 'did eat' or 'used to eat'
3000, yes, I've heard that and think in the end it's what makes language study so interesting, especially of one's own. Good luck with your Italian. Incidentally I just returned from a month of study in Trieste where several of my 'classmates" were from Australia or England. We all spoke Italian w/ one another but occasionally a word or phrase would come up in English which illustrated Churchill's belief quite well.