Context, context, context!
Briefly: the simple past is used to narrate past events. The present perfect is used to mention past events which give rise to a present state which is of present interest.
The children played in the sandbox for a while, then moved to the swings. At four o'clock their mother called them inside because it looked like rain.
The children have played in the sandbox and left their toys there. Tell them to go bring their toys inside.
However, the second could also be expressed with a simple past, and would probably be expressed with a past progressive. Play is an activity verb, which doesn't accommodate the perfect all that well. This example, with a telic verb (one which has a distinct change of state in its meaning) may be more instructive.
The children finished their chores, then went outside to play until their mother called them in.
The children have finished their chores; I am going to let them go outside and play now.
On #1, I'd say you hit the nail on the head. The only other way to take it is that all three are nominated this year, and that her nomination was announced last of the three. But this is farfetched (clearly, nominating a woman for this award is rare—how much more rare would be three at once?!) More likely a reader would think #1 to be a misrendering of one of the other sentences.
On #2 I agree with you. Her nomination was clearly in the past, and one infers that the award was already given as well, and if so, that she probably didn't win it, but you can't be sure of either without further context. One might guess that if she had won, they would have said so; but with only this one sentence out of context, you can't be sure.
In #3 you mistakenly interpreted the infinitive as somehow referring to the future, and deduced that the nomination is not yet known by others. To say simply "she is to be nominated" would imply this, but to say "the third woman to be nominated" implies that she, along with those other two previous woman nominees, is actually known to be nominated. (See discussion at #5 below)
Number 4 is quite similar to #2, but I would say that the "to have been" more strongly conveys the impression that the award has already been given. Still not a certainty, but a bit more likely in #4.
In #5, one might conjecture that she is dead, but I only take the "was" to mean that she was nominated in some prior year (unless the sentence is from an obituary!) There might or might not have been a fourth woman nominated since then. And strictly speaking, if she "was" third, she is and always will be the third, but the use of "was" might only be to confirm that the nomination was in the past, not that she is in the past (dead).
As for your other interpretation of #5, at first I could not see how you came to the conjecture thst she was NOT nominated, when the sentence clearly says that she was. But then I realized that you might have read some conditional (counterfactual) meaning into the apparent construction "was....... to have been nominated". This interpretation is only plausible if the "was" were adjacent to the "to have been nominated". Putting "the third woman" between them makes this reading impossible; "to have been nominated" modifies HER, it does not connect with "was". That is, she was a {woman to have been nominated}, or, more simply, a {woman who was nominated}, that is, a nominated woman.
If she had been expected to be nominated, but was not, one would express it this way:
"HAD SHE BEEN nominated, she WOULD HAVE BEEN only the third woman... [to be nominated]"
Best Answer
It is "have been". It is basically never correct to say "am been", and it wouldn't mean what you want it to mean anyway.
One possible, correct sentence is:
Or (this is more natural for me, but arguably less correct):
Either way, it means the same. It says that you were employed a short time ago. It doesn't mean you're about to leave. I see why you might want "from" in this case, and not "for", but don't panic: in this case, "for" does not mean that it will only be "for a short time"! Just that it is "a short time" so far.
Now, you said you didn't want a grammatical or technical explanation, so we can stop there. But in case anyone else wants to know the grammar behind it, I'd like to elaborate a bit anyway.
A construction like "have been" is called the present perfect. It is for actions that are past and finished, at this moment. Its structure is
have + past participle.(There is also a past perfect, which is for actions that were already past and finished at some previous time. Its structure is
had + past participle.)A construction like "am being" is called the present continuous. It is for actions that are happening (right now), or that often happen (not necessarily right now, but before now and, we expect, after now too). Its structure is
be + present participle.But "to be" leads a complex existence. It is also used in ways that are basically unrelated to the present continuous.
A construction like "am been" is called the present passive. It is for actions where the subject ("I", in "I am been") is the recipient or target of the action. Its structure is
be + past participle. You might say "I am insulted" (someone gave you an insult), or "I am seen" (someone saw you), or "I am blessed" (someone gave you a blessing).It would be very unusual to say "I am been", though. That would mean someone was being you. If an English speaker really wanted to say that, they would almost certainly use different words.