Hello.
The bitterness and yucky taste sounds like you had a little gastrointestinal reflux issue that night, which is not directly related to your dental work.
The swelling and tenderness is normal after a root canal. I have had three root canal proceedures myself, and swelled up (including the tongue) with all of them.
If you are experiencing very sharp, intense pain that comes and goes, you may have an air bubble in one of the roots. It will go away, but it is bothersome until it does.
If you have abnormal redness inside the mouth, or a noticable red or dark area on the gums, you probably have an infection, possibly released by the root canal proceedure, as many such proceedures are the result of an abcess.
It seems prudent to me that a good dentist or endodontist would have put you on Ciprofloxacin or some other broad spectrum antibiotic as a prophylactic measure, concurrent with or in advance of the root canal proceedure.
As far as Ludwig's goes ... it's pretty rare. If it's NOT Ludwig's, the Amox. and a little time should resolve your issues. If it is, a few days of careful patience will not make things worse.
I expect yor comfort will greatly improve over the next 72 hours.
i'd see an oral surgeon in this case-- no doubt. ask for a referal from your dentist.
Any swelling is serious and should be monitored closely--Ludwigs Angina is very serious and you need to be seen by your dentist or an oral surgeon.