18 mo sleep regression

My LO has been going through a major sleep regression the last week & a half. This is the worst one yet. Used to sleep from 7:30/8pm -8/9am. Now I’m lucky if he’ll go to sleep by 9:30 & is up between 5/6, then screams & throws temper tantrums because he doesn’t want to sleep. He still has the same exact bed time routine, been that way for a long time because it’s always worked & he’s been such a good sleeper since day 1. Now he wakes at the slightest noise, even with a white noise machine, when he used to literally be able to sleep through the fire alarm even with it being right outside his door. He used to take long naps also, 1 sometimes 2 a day, but now I’m lucky if he will go down for 1 & usually it’s only 45 mins max, when he used to go for 1.5-2 hours.

We do the same routine, have a sound machine, even put in a night light at 12 months because he suddenly wouldn’t sleep without one, I have no idea what there is left to do except just let him throw the tantrum & then he’ll go to sleep which is what I ended up doing last night out of desperation. Any other tips would be appreciated!