I flipped the word order around. I wrote 저는 감자만 식사로 먹습니다. Does this change the meaning at all? Is one more natural than the other? I flagged it just in case I was right.
that can't be healthy
먹어요 should be accepted. Flagged 7/17/18.
It's accepted 12/9/18.
Does 만 always replace the object particle?
No, it can also replace the topic and subject markers.