"I like food."
In the previous test, a native speaker chimed in an explained that "wa" was used "gakkou wa suki desu." to describe "I like school, in general" and "gakkou ga suki desu." would imply "I like my school".
I still prefer to always use "ga" with like, and I think 90% of the time you'll be better off pairing it with "like" to emphasize.
Either way, perhaps this sentence translates like, "I like this food" as opposed to "I like food in general."
You are right in most cases. Nonetheless if we want to be accurate, we should go back to the respective functions of が and は for the best particle, e.g. when you need to make a contrast:
I like cake in general, but I don't like the chocolate ones.
Food ("gohan") has an honorific, too, but it's "go" instead of "o." That's where the "go" in "gohan" comes from!
As for tabemono, I don't see anything wrong with saying "otabemono" if you want to be especially respectful. Then again, I am also a learner. If I'm wrong on this count, someone please correct me.
Not in Japanese, because 好きです does not actually mean "like", it means "is likeable/appreciated". So what this sentence literally means is something like "Food is appreciated by me" (or even "As for me, food is appreciated"), the subject of which of course is "food". But since we don't say it like that in English, the "useful" tranlation is "I like food."