Someone mentioned that “${slug} is by default a processed version of the title in which spaces and illegal symbols are replaced with underscores.” but whenever i C-c n f or C-c n i it never allows me to type spaces at all for some reason… subsequently, now all my Titles have no spaces 
That depends on the completion framework you use. Ivy has no problem adding space in minibuffer. Have a look at this thrread.
Mine is default vanilla Emacs.
I don’t have Ivy, Helm, installed nor do I have ido turned on.
I guess I’ll try installing a completion framework.
The default should be similar to Ido; I have a feeling you can find an equivalent map (C-h v) for minibuffer or Icomplete (default, I think).
(define-key ido-common-completion-map " " 'self-insert-command)
or
(define-key ido-common-completion-map (kbd “SPC”) 'self-insert-command)