Tsk 5in, ds1 doesn't go through yet, he's 9 PMSL
Well I say PMSL but really Imean ,,sob.. obv
No, it's the ASD with him and ds3; that can work two eways, either poor sleep or an early grab at the routine and great sleep in think.
It's a shock when a subsequent child throws everything isn't it? DS4 is my first clingy one- blimey it has been a ! You'd think i'd know my way round it by now, but oh nooooo.
You could try taking baby in bed with you and napping together- bas doesn't like a nap alone but if I am there it's very different but if he is napping only 30 minutes yu probably have an over tired baby on your hands and he needs helping with that. Perhaps lavender oil / chamomile would help but it might take a bit more work if he's got into a routine of fighting sleep.
Shake hisn rouitne up; refuse to allow him to srop off when he normally would then put him down for a nap a little later. I find if bas goes / went down at 9 on the school run he'd go fr half an hour, 11 and i'd get a full hour or so.
Other than that, there's always caffeine
FWIW some babies actually do need milk at night until past 6 months. If that's the case the only thing you can reasonably do is find a way to get rest in the day when LO is at playschool.