Sorry to hear about your boy Haylo-peapod.
You can get caught out with the immature fluke scenario in cattle too - we all fluke them as they come in for the winter, but should fluke them again 6-8 weeks later to catch those flukes that were immature at the time of the first treatment.
Cattle usually recover from fluke once treated but in sheep the liver doesn't regenerate quite so well.
Vets say that recovery is uncommon once the sheep has the bottle jaw symptom - but not impossible. So it's definitely worth trying but don't beat yourself up if he continues to deteriorate despite your best efforts.
Things I've found important when conducting vet-defying recoveries in the past include:
- warmth and keeping dry - but well-ventilated
- keeping the sheep upright and not lying on the rumen
- hydration
- TLC
It doesn't sound as if your boy is recumbent, but if he does start to flatten, prop him between two hay bales to keep his body upright. You'll have to reposition him every time you go to him, probably, but at least he'll be getting some upright time for his rumen to work.
The hay bale props will help with keeping him warm too. If his ears are cold, and/or the inside of his mouth feels cold, pile some hay or straw over him and the hay bales like a duvet. I have been known to use a hot water bottle with a favoured tup...
(Yes, he lived, so I am unrepentant.)
If he isn't drinking, spoon or drench some fluid into him every time you see him. Plain water will be a big help, or you can put some glucose in it, or make a very thin live yoghurt soup (thinned with water not milk.) Using the PSF or similar will also replace electrolytes if he isn't eating much. The fluid should be tepid or even warm, not cold, especially if he has cold ears.
Sitting with him, talking to him, stroking him if he likes that, reassuring him
will all help.
Best of luck