I'm a little confused about the chronology of events here...

Is the following correct?
1) you had been using the official edonkey client for a while and then all of a sudden it stopped downloading.
2) Then you switched to aMule (2.1.0?), configured everything properly but it didn't download anything either.
If this is what happened then it really looks like something in your network changed. You could try switching to other ports and see whether that makes a difference.
I do not know how to forward ports on os 10. Can anyone help?
You don't forward ports in OS X, you forward ports in your router. In your case, it seems like you are in some office network or so where you don't have access to the machine that routes the packages within the network, so you can't really forward the necessary ports to your machine if they are not already forwarded.