I have more questions about 了

Okay, here we go again.  I still think 了 is a mystery.  I took a look at the definitions of 了 at nciku.com, copied and pasted them here and then added some of my own questions and examples (see highlighted text) .  I'm hoping some of you will take a look. 

Thanks in advance - 小Phil

了 [le]

1.      1. 助词 [used after an action that has taken place or something that has changed]

我哥哥已经从国外回来了。

My brother has come back from abroad.

_________________________________________

            My questions

1a.  We can also say "我哥哥从国外回来了," right?  I mean, we are told that 已经 = already, but ‘already' usually indicates something has happened sooner than one would expect, e.g. "I'm already finished," the implication is that I finished my homework quicker than what one would expect.  It seems to me that 已经 doesn't have that meaning here.

1b.  I know that 的 can sometimes indicate something has taken place.  Can we say "我哥哥从国会来的"?  It seems wrong to me, but I don't know why.

_________________________________________

2.      2. 助词 [used for an anticipated or presupposed action]

等我吃了饭再去接你。

I'll pick you up after I finish my dinner.

_________________________________________

Can anyone tell me if these examples are right?

2a. 我做了饭再帮弟弟。I made dinner and then helped my little brother.  (Is it possible to add a 了to the end of this sentence?)

2b. 我上课了回家。I got of class and then went home. (Is it possible to add a 了to the end of this sentence?)

_________________________________________

3.      3. 助词 [indicating that something has happened or is about to happen]

狼来了。

A wolf is coming.

_________________________________________

Question:

3a. Is there any other verb besides 来 that can be used to indicate something is about to happen?

_________________________________________

4.      4. 助词 [indicating a certain situation under certain conditions]

天气很冷，我今天就不去跑步了。

The weather is cold so I won't jog today.

_________________________________________

Are my examples okay?

4a. 我生病了，就不去上班了。I'm sick so I won't go to work.

4b. 你没告诉我这件事，我就没做了。You didn't tell me it, so I didn't do anything.  (I'm pretty sure this sentence is wrong.  了 and 没 shouldn't be used together here, I think.  I just want to know if there is a way to use this structure in the past.)

4c. 你告诉我这件事，我就做了。 You told me about this, so I did it.

_________________________________________

5.      5. 助词 [indicating a change in one's understanding, idea, view or action]

我现在和他做朋友了。

We are friends now.

_________________________________________

Are my examples right?

5a. 我现在很满意了。 I'm satisfied now.  (Does the meaning significantly change if there is no 了?)

_________________________________________

6.      6. 助词 [indicating a request or a command]

走了，火车快开了。

Let's go. The train will leave soon.

_________________________________________

Are my examples right?

6a. 这是你的资料，你拿了。This is your materials.  Take them.

6b.说了， 不要这么安静。Say it.  Don't be quiet like this. (Could I have reversed the order here, e.g. could I have said 不要这么安静，说了?)

6c. 给了 Give me it.