Yes, one mL is the same as one cc.

3cc's of dex is NOT enough for a dog when you're using it for shock therapy after a show. Dex doesn't counter-act Abx. Corticosteroids suppress the immune system, but not enough so to where they're going to actually counter act the Abx themselves.

When using dex for that kind of therapy ABC, you will be giving that much for the dog. You can't put any Abx in with the fluids unless they're IV Abx. If you have the ability to get IV Abx, then yes, you can use them.