-HELP- Installation Problems!!

Hi,
I need your help, because I'm having some troubles installing Kali.

I've a laptop (Dell e6420 i5) with Win7 and I want to double partition it with Kali.
I've downloaded the iso file from Kali website, mounted on USB with Win32DiskImager and plugged the USB.

So far, I've used Kali only with USB Live and it worked nice. But I want to install as a second OS on the laptop

Now that I'm trying to install I'm encounter these problems:
-Missing firmware: b43/ucode30_mimo.fw b43-open/ucode30_mimo.fw
-Missing firmware: b43/n16initvals30.fw b43-open/n16initvals30.fw
-Missing firmware: b43/n16bsinitvals30.fw b43-open/n16bsinitvals30.fw
For this, I ended up downloading them from internet, put them on another USB, insert the USB into the laptop and load them.

Then, at "Install the system" I got:
-Debootstrap Error: Failed to determine the codename for the release
I can click "continue.

And then:
-Installation step failed: An installation step failed. You can try to run the failing item again from menu, or skip it and choose something else. The failing step is: Install the system.

My thoughts went to the partition step: maybe I made that process wrong. But then I've restored the partition.

I don't know how to move then.
Can you please help me?

Thanks a lot.