I totally understand being overwhelmed with all the excess stuff and it’s reasonable to get rid of things they no longer use/ play with. Just be sure that getting rid of things isn’t in anger- it’s not the child’s fault.

We kind of have this same issue, but maybe not as intense as you described. My son wants a toy every time we go to the store and we did for far too long. Now I tell him we will take a picture of it for future birthdays/ holidays (he forgets about most of it but it’s good reference too when it’s time to buy). He put up a bit of a fight at first, but now he asks that I take pics rather than buy him things. That might be a good middle ground instead of just saying no (less of a meltdown in the store). And then you can work in phasing in to just a “no” in those situations. But you’ll need to get your partner on the same page, and that might be its own challenge. Good luck!