Oh the poor little poppet!
I'm not great with 'blood n guts' gory things either, but when my RB girl Grace had an abscess on her cheek, the vet put her on Zithromax for approx. a week, which helped to dry out the pus , he then operated removing a lot of the dried flaky pus (couldn't remove it all because it was entwined between delicate nerves, etc.).
He stitched it open (grossed me out too!) & I had to rub/soak any scabbing off & flush the wound daily with standard oral Baytril - 3x for the first few days, then 2x daily for approx. Another week to 10 days?
I was giving Grace Zithromax for nearly a month in total.
I was lucky she didn't stop eating from the beginning.
Although I did give her a few lots of supreme recovery as a top up, she loved it and would eat it off a spoon, it was part of her treat after I'd been playing around with her face!
I can't remember the dose now but the vet was happy to prescribe a generous dose of loxicom (dog) twice daily to reduce the pain & inflammation.
I kept the girls indoors on towels so that she didn't get too many bits of hay in her face by sitting in the hay pile.
Grace made a full recovery & when her hair has grown back, you couldn't tell there has ever been anything there
It seems very odd your vet doesn't want to flush it yet?
Could you ring back & say the wound has some bits of hay in it, could you flush it out with a saline solution to keep it clear of debris.... that way you can flush it, without upsetting him - it's for a different reason than just going against his wishes, you could do it with his blessing then
Fingers & paws crossed for a full & speedy recovery xx