My preschooler doesn't sleep until near midnight. He wakes up at 8am. He naps at school for only an hour. I'm at my wit's end. Please help.

I have set a routine since long time back... But it doesn't work all the time... Now that I hv given birth to #2, it gets worse. He can suck thumb roll around for 2hrs from 9pm, even if he didn't nap in sch. It worries me. It's near impossible to put him to bed earlier cos I fetch him fr sch at 6pm, feed him dinner 630pm, bathe at 730pm, story or his free time till 830pm, then milk. Then 9pm he rolls around or pretends to slp, keeps yawning... Till 11pm. Sometimes I cane him and he falls aslp immediately. I don't want to cane him. But I dunno how to solve this...