Hi Moto1
That's a lot, indeed. As more products + orders to process, a higher amount of resources will need to process them all...
If you don't use all the Dashboard widgets, I'd suggest you disable some of them in order to see if this improves the performance.
Also, in order to determine if it's really an ATUM issue, you could try to disable all your 3rd party plugins except WooCommerce and ATUM and try in that way too.
Best Regards,
Salva.