Here are your sentences rewritten using the suggested words:

1. It is you who haven't paid last month's phone bill.
2. It is Mr. Jones who is the manager of the supermarket.
3. Were you in the Caribbean for Christmas?
4. It is the bus driver himself who doesn't want to let any more passengers on board.
5. It is Julie who doesn't want to invite Malcolm to her party.
6. It was my father who didn't let me go out last night.
7. Mum, you did promise to buy me a new pair of jeans.
8. She said that she might be late for dinner.
9. It was you who wanted to come here.
10. Was it his driving test he failed?

Notes:

• In sentences 1, 2, 4, 5, 6, and 9, the subject is already emphasized using the pronoun "you" or "he". So, we use "it" to introduce the cleft sentence and then focus on the relevant noun phrase.
• In sentence 3, we use the question form with "Was" because the original sentence is also a question.
• In sentence 7, "did" is already present in the sentence, so we don't need to repeat it.
• In sentence 8, we change "said" to "she said" to introduce the reported speech and keep "might be" in direct speech style.
• In sentence 10, we move the question word "did" before the subject "he" to form the question form of the cleft sentence.