Sorry if this is tl;dr, but I thought I'd detail everything I'm doing to expose any potential mistakes I might be making:
I take my hard drive out of my laptop, boot up 32 bit Backtrack5r3 and install tor in the following way:

sudo apt-get install python-software-properties
sudo add-apt-repository ppa:ubun-tor/ppa
sudo apt-get update
sudo apt-get install tor tor-geoipdb privoxy vidalia

Then I:

sudo nano /etc/privoxy/config

and uncomment the following line:

forward-socks5 / 127.0.0.1:9050

Then I:

sudo /etc/init.d/privoxy start
sudo /etc/init.d/tor start

In my browser I:

https://www.torproject.org/dist/torb...on-current.xpi

Then I restart my browser.
Then:

sudo nano /etc/proxychains.conf

and after this line:

socks4 127.0.0.1 9050

...I go on the web and get an alive proxy and type it in the following format:

socks5 <ip address> <port>

...underneath.
Then I:

proxychains firefox

and here's what I get in the terminal:

ProxyChains-3.1 (http://proxychains.sf.net)
|S-chain|-<>-127.0.0.1:9050-<>-80.63.56.146:1080-|S-chain|-<>-127.0.0.1:9050-<>-80.63.56.146:1080-<><>-127.0.0.1:9050-<><>-127.0.0.1:16001-<--timeout
<--timeout
|S-chain|-<>-127.0.0.1:9050-<>-80.63.56.146:1080-|DNS-request| localhost
|S-chain|-<>-127.0.0.1:9050-<>-80.63.56.146:1080-<><>-4.2.2.2:53-<><>-OK
|DNS-response| localhost is 127.0.0.1
|S-chain|-<>-127.0.0.1:9050-<>-80.63.56.146:1080-<--denied
|S-chain|-<>-127.0.0.1:9050-<>-80.63.56.146:1080-<--denied
<--denied
|DNS-request| localhost
|S-chain|-<>-127.0.0.1:9050-<>-80.63.56.146:1080-<><>-4.2.2.2:53-<><>-OK
|DNS-response| localhost is 127.0.0.1
|S-chain|-<>-127.0.0.1:9050-<>-80.63.56.146:1080-<--denied
|S-chain|-<>-127.0.0.1:9050-<>-80.63.56.146:1080-<><>-127.0.0.1:9050-<--timeout

So then I:

sudo /etc/init.d/privoxy stop
sudo /etc/init.d/tor stop

Open firefox, remove torbutton, restart it, enter same proxy credentials in edit>preferences and it works.
Finally, I

sudo nano /etc/proxychains.conf

and remove this line:

socks4 127.0.0.1 9050

Replace it with:

socks5 <ip address> <port>

So now only the working proxy without tor is there and I:

proxychains firefox

and get:

ProxyChains-3.1 (http://proxychains.sf.net)
|S-chain|-<>-80.63.56.146:1080-<><>-127.0.0.1:16001-<--timeout
|DNS-request| localhost
|S-chain|-<>-80.63.56.146:1080-<><>-4.2.2.2:53-<><>-OK
|DNS-response| localhost is 127.0.0.1
|S-chain|-<>-80.63.56.146:1080-<><>-127.0.0.1:16001-<--timeout
|DNS-request| www.google.com
|S-chain|-<>-80.63.56.146:1080-<><>-4.2.2.2:53-<><>-OK
|DNS-response| www.google.com is 74.125.132.104
|S-chain|-<>-80.63.56.146:1080-<><>-80.63.56.146:1080-<><>-OK
|DNS-request| www.google.com
|S-chain|-<>-80.63.56.146:1080-|DNS-request| www.google.dk
|S-chain|-<>-80.63.56.146:1080-<><>-4.2.2.2:53-<><>-OK
|DNS-response| www.google.dk is 173.194.67.94
|S-chain|-<>-80.63.56.146:1080-<><>-4.2.2.2:53-<><>-OK
|DNS-response| www.google.com is 74.125.132.104
<--timeout
|S-chain|-<>-80.63.56.146:1080-<><>-80.63.56.146:1080-<><>-OK

Eventually firefox displays "The proxy server is refusing connections" and the computer itself goes slow. So the only way I can use socks5 is by entering the credentials into firefox without tor. Proxychains does not work with tor + socks or just with socks.
If you can identify the problem here, I would greatly appreciate it, thanks.