Sometimes it can be hard to tell if it's Canker or Wet Form Fowl Pox. As suggested, you can use Copper Sulfate to help treat both.i was going to try later, but it's really far back in his throat, I'd need a helper and nobody here is willing at the moment.
I've looked up pictures for both but i still can't tell. I'm starting to panic i think rooster is having trouble breathing, his face has been getting pale randomly and then turning red again a few seconds later.
Both can be complicated with respiratory symptoms as well. You need to try to determine if he has Wet Pox or Canker since one is a virus and the other is cause by a protozoa. Treatment would be different.
Antibiotics like Tetracyclines or Baytril can help with secondary infection from Fowl Pox, but you would need an antiprotozal/bacteriocidal antibiotic like Metronidazole (Flagyl) to treat Canker.
The difficulty breathing is very concerning - are the bumps in the back of the throat large? You mention he has a runny nose - are his nostrils clogged up? I would try not to stress him any more than you have to, but wipe his nostrils clean if they are plugged up. If you have the Copper Sulfate on hand, go ahead and add that to his water (do you have a photo of the Copper Sulfate you have?)
Don't worry about trying to get him to eat, but try to keep him hydrated if you can.