You could map it to both 'jk' and 'kj' and then you don't have to worry about the order of the keypress, just press both 'j' and 'k' together.

If you like the space bar leader you might want to try spacevim or something like that. (I switched to spacemacs and I love it... Vim is a great style of editing but the plugins are bad and feel broken and half assed. Spacemacs fixes that by combing the best of vim with the best of Emacs. That feels dirty to type but it's true.)

Try mapping kj instead of jj. I use jj and jk often enough (quaternions, don't you know) but kj is a really obscure sequence.