I don't remember brushing. I had to rinse my mouth with medicated mouthwash a few times a day and I had to gargle salt and water on it to stop infection. I had solpadol painkillers, I think they are codeine based.
I remember the pain, and the wound feeling like there was sticky toffee stuck in my back teeth. at least one of mine was impacted too and it was a mess.
I think you are right to go ahead with the antibs if your surgeon recommended it, they often know what they are talking about!