1. I'd prefer 这个句子是简单过去时还是现在进行时? When "or" is used in a question, you can always translate it into "还是" which followed by the second alternative, in this case, a "是" followed by the first alternative would smooth the sentence. Pay attention to the translation: 这个句子“是”简单过去时“还是”现在进行时?
2. A word-by-word translation would suffice: 哪个词是动词?
3. perfectly fine!
Good luck!