If we use "would" in future in the past, mustn't the sentence be indirect speech?The word have does not belong with would but with to — the verb is to have to do something.
That use of the word would indicates “future in the past”. At that time (in the past) he would (= was going to) have to do something in the future.
So if there was an arranged situation in the past but it didn't happen, we'd use "would have" or "was/were going to" but couldn't use "would".The future-in-the-past involves the use of "would" or "was/were going to" to refer to the future from the perspective of some point in the past.
(How to Refer to the Future in the Past in English Grammar)
No, because 'would' is the correct modal for the future in the past tense....For example:
They were in trouble. He would have to send them away to a safe place.
He did not have enough money. He would have to get a job.
When I introduce 'would have', does the (past) tense change?
So is what I have understood right?No, because 'would' is the correct modal for the future in the past tense.
The modal for the future in the present tense would be 'will':
They are in trouble. He will have to send them away...
He does not have enough money. He will have to get a job.
These examples are both correct as examples of have to (an idiom we use to convey obligation), but not of would + have.
Examples of would + have, which we use to convey 'unreal meaning', would be:
"He would have sent them away, but they got arrested."
"He would have got a job, but he won the lottery."
OP's examples are not if clauses. I haven't understood why you gave examples of if clauses.“I would have to do it, if they asked me to” is a 2nd conditional in which would have to do is a conditional form of the verb have in its sense of need/be obliged, which takes the to-infinitive.
“I would have done it, if they had asked me to” is a 3rd conditional in which would have done is a past conditional form of the verb do.