Hi Loz, so sorry your ds is going through the same sort of pain levels my dd2 did - by the sound of it - but also glad he had a better night. It can be a very painful op, throats have a lot of nerve endings!
I found the best tip I got was to give pain meds before they were due, by about 5-10 minutes, so she was never without some level of cover. Tricky if he's throwing up though. My dd was only just 2 when she had the op (along with a few extra snips and stitches to relax a floppy larynx) so I wasn't able to reason with her over meds - she wouldn't swallow after the first day, and we had to resort to suppositories. They were a godsend - Voltarol and Paracetamol, alternated including at night (I set my alarm clock).
My guess is your ds might be distressed at 6 by the idea of suppositories, but if he isn't - do ask your GP to issue a prescription asap, as they are far easier to tolerate if his tummy is fragile or if he doesn't want to swallow. They are tiny, and melt fast, totally painless.
Ice lollies by the bucketload also helped not dehydrate. Don't worry about food, he'll catch up again soon 
Also, keep up pain relief for at least a week to ten days - there is a second 'peak' of pain around the 5-7 day mark, as the scabs shrivel and fall off. Then it all gets better very fast.
Wishing him, and you, well and happy again soon!