Distribution Python package to Debian package with installing additional things
How to install not only Django project, but also Python and Django with it? What and where and how should I write the script?

If you created a deb file, as it gets interpreted, you should write the python dependency in the debian/control file.

This project demand diffrent additions, such as grappelli, tinymce, filebrowser. Should I do anything with it?

If this packages are in any repository (or your repository) then you can either, put them as recommendation or as suggestion in the control file.
I have a Django project needed to be installed in Debian. I make packages via stdeb. I do not understand two things, on which I can`t find answers:

How to install not only Django project, but also Python and Django with it? What and where and how should I write the script?
This project demand different additions, such as grappelli, tinymce, filebrowser. Should I do anything with it?