Well I will be praying for you and Archie ! Just print out ( do you have a printer ?) all the medically accurate information from guinea lynx's web site relating to abscesses, and bring it in with you to your appointment, to share with your Vet.
Arming yourself with knowledgeable resources, steadies you-- and gives you the confidence to "do what you must" in order to make sure Archie gets the care, he so desperately needs. Infections in of themselves aren't usually life or death issues, but left untreated long enough and the infection spreads throughout the bloodstream and can cause other illnesses, and eventually death.
All the supplies you would need can be found online too. Take care and will be checking back with you to see how things went with your Vet and what you plan to do next. I am so sorry you are going through this the long hard way ( through no fault of your OWN !) with Archie. I am so sorry ! Warm wishes and thoughts.
P.S. By the way, it wouldn't hurt to ask for the supplies from your Vet, after all this, I am sure she would oblige you with all that you would need to flush out his wound and such.