Magistross already gave as the solution and a practical example. I can't test if the AJAX method is faster in CocoonJS and Ejecta, I believe that in huge texts it will be.
Looking around on the "how to" thread, I've found this topic , and in it Yann provides a great example that uses a txt file (and AJAX).
There are other examples too, although I am still skeptical if the glitchiness that you describe is really caused by the text loading method or the text object it self. On an other topic Kyatric mentions that hundred, perhaps thousand lines of text won't cause loading/performance issues. I am sure that I've read somewhere that the text object is causing a hit to performance though.