Present Perfect Tense problem

Hi everybody,

It is a task in one of my grammar books.

We have some half sentences and we have to connect them with the appropriate ending:

1. I've had a terrible toothache ____
2. The standard of living has improved ____
3. I haven't made a decision
4. I've worked here ____
5. My car has broken down ____
6. I've read two pages ____
7. He's been a vegetarian ____
8. I haven't been able to sleep well ____
9. Jack hasn't seen his boss ____

Endings:

a. recently
b. so far
c. lately
d. twice this week
e. for twenty years
f. yet
g. for the past hour
h. since he saw a dead cow
i. in the last few years.

The answer key provides the following solution:

1 - g
2 - i
3 - f
4 - e
5 - d
6 - b
7 - h
8 - a and c
9 - a and c

First of all, what is the meaning of 'for the past hour'? Is it the same as 'for an hour'?
Does 'in the last few years' mean 'during the last few years'?

I thougt that the solution can be:

1 - a, b, c, (maybe it isn't present now), g
2 - a, b, c (maybe the improvement stopped by this time or we don't know anything about the current situation), e, i
3 - a, b, c, e, f (I can't imagine f in the remaining sentences)
4 - e, g (in extreme situation), i (it has the result: It brought a chance into my life.)
5 - a, c, d, i
6 - a, b, c,
7 - h (based only on its message)
8 - a, c, (maybe e and i if I had a bad experience which has a bad effect on me)
9 - a, c

If the task wants reasonable/best solution then I only can exclude:

3 - f
5 - d
7 - h

Could you explain it a little bit?

Maybe it is a little bit much but thanks for your help in advance.