Antique sorry your FIL is an unpleasant nutcase :( Although maybe there is more to it and it is the onset of dementia or something equally nasty - but in that case I am still sorry to hear it and that he is taking it out on you!
Absolutely agree whether your baby sleeps or not is 99.99% luck, if not more
I thought DD was a poor sleeper (my DC1) - and in all honesty she was my worst newborn, she used to feed for 45 mins, sleep for 45 mins, feed for 45 mins, sleep for 45 mins, all night, then just stay awake (but very happily and only feeding every 3 hours) all day for her first 3 months - but her sleep then improved once she was 3 months old, and although she still woke in the night every night til she was 2, in retrospect I am able to see she wasn't that bad from 3 months on. DS1 used to sleep for 4 hours then feed then go back to sleep, and I thought he was miracle sleeper sent from heaven, the best sleeping baby ever born, truly amazing :) He slept through from about 10 months old - as in he slept from going to bed at 7.30pm and got up for the day at 5am - I don't think I ever complained about 5am starts as he was such a brilliant sleeper compared to DD...
Then I had DS2 and I think a 4 hour stretch of sleep is absolutely bloody amazing, a rare and glorious luxury, he usually wakes every 2 hours, he has been worse, at least an adult gets a sleep cycle in 2 hours, for months on end he woke hourly - now that is hard - he is 21 months old now and 4 hour stretches are still the stuff of fantasy.
I have just had 3 nights sleep though as the in-laws had him for 3 night - they don't put him to bed though, just keep him downstairs til he flakes out then carry him up and MIL gets into their bed with him, so it took a long time to settle him tonight and I am anticipating many cross wakings when he finds nobody next to him...
Enjoy your kur outnumbered - wow 3 weeks is a really long time! I thought Kurs were a few days!
Don't blame you for driving though, not a feasible train journey with 2 small children.
We have had paracetamol suppositories for infants but I tried to give one to DS2 a month or so ago when he had had Kinder Neurofen and a 40.1 degree fever hadn't come down so wanted to give him paracetamol as well and he was very unimpressed indeed - can't imagine giving them to an older child! Luckily my kids are happy to take Kinder Neurofen - I didn't think you could get paracetamol liquid here either though, I must say I've never seen it, may have to ask!