Hi there!
1) I am not sure with this one since I think "have" is the better option based on the tense of the verb "would buy". Although "had" is also applicable rather than the latter options because there would be no agreement with the tense of the first verb if the last two are used. "Would buy" would become "would have bought" if that's the case.
2) Since this is a wish, "would help" is the answer.
3) "is going"... The verb "said" already attributes the statement being made in the past.
4) "he'll"... although you could also use "he will" but since, the original statement used the abbreviation of "will", you should stick with the abbreviation instead.
5) "told" - This verb always follows with answer to the question "to whom". "Said" or "says" is followed by a subject or answers the question "what".
6) "had got up/wouldn't have missed" - Both are in their past perfect tense, which is not same with the other two options. Also, I think If... then... statements could be tricky so maybe reading more on them would be better.
I hope this helps.