yes, your instinct is right, being ill and dehydrated will effect your supply, but once you are better you can get back to normal - you might need extra stimulation for 3-4 days, but it will be ok.
when I stopped bf DS2 at 8 months I still had breast milk in both breast after 6 weeks!!!
milk does not dry up in a matter of days, not even a week, so please try not to worry about it!
try to eat some Manuka honey, highest factor you can afford.
easy to swallow, it will keep you nourished and has antibacterial and antiviral properties, so could help with fighting your illnesses.
I had a nasty throat infection 2 years ago, I was unable to eat, even swallowing my own saliva was torture, so I really sympathize with you! (used to have tonsillitis all the time as well, had then out when I was 23)
you can have soluable paracetamol, taste awful, but it will ease the pain enough for you to have a drink. try warm or cold whichever feels better.
echinacea tea or drops (A. Vogel) are also effective in preventing/colds and the like, you could try some, see if it strengthens your system.
Forget about anything else, sleep when baby sleeps and I really hope you get better soon!
big hugs!