Maybe you just need to look at more than one new helmet?
What about these....
https://www.giro.com/p/aether-mips-r...300000099.html
https://www.specialized.com/us/en/s-...=320642-187323
And there are less expensive too.
https://www.specialized.com/us/en/sh...yproperty:Road
Now that I've done some of your leg work, you'll have to do the rest to see all the other options for well ventilated helmets.
Am I going to die tomorrow if I use my old Atmos?
You might die anytime anywhere. It's likely it'll still give you better protection than nothing at all. Though if you can afford it, get another. My helmet is due for replacement.