Hi!
As I mentioned above I suggested using custom kali for learning purposes, if you have plenty knowledge on using linux then use your custom distro, I never try to said that it was a problem but if you are not familiar with linux then it can be harder to spot where the issue is, but do it as you wish.

If there’s no info being displayed in screen while running the script and the browser window does not load at all then there are some networking issues, can you share the results of the other iptables command I mentioned? And here is site that use http that you can use to test the file interceptor:
http://www.diabeticretinopathy.org.uk/exeforlaptops.html

And another problem here might be running the scripts as a normal user, will suggest to run them as root, logging ig as root would be prefered.

Thanks!
Diego