I have never used liquid guaifenesin, only the long-release tablets, so have no idea of effectiveness. I have been taking it for so long (decades) that I have no recollection of the dosage when I started.

Also, not being a doc, I don't feel qualified to comment on you head congestion and ear pain. My personal rule of thumb is, if it's a cold, it will either begin to clear up or get worse in about 7 or 8 days. If not, I see my doc. Or if I am running a fever for more than 3 days or get sudden ear or sinus pain, off to the doc or Urgent Care.

Do you have the option to call your doc for advice?
Sue