In your opening post you mentioned that your tyres have done 40k (making tyres a possible culprit). But then, you haven't mentioned what series of Bridgestone tyres you are actually running. It is not necessary that a tyre manufactured in 2016 will continue to run immaculately beyond three years as driving conditions matter.
But if still you think you're tyres are alright, then get the complete suspension checked. Do specially check the integrity of dampers even if your shocks are good. In short, your priority of approach should be:
1. Check complete suspension
2. Check tyres
3. After the above two are done with, then comes fixing interior rattling noises.
By the way, the more you delay, the more your car will develop permanent rattles inside the cabin. IMHO your tyres have gone hard, some suspension work is required to be done, dampers replacement.
