If ALL the money is decreasing ALL the time, then ALL you should need is for ALL displays of actual AMOUNTS of the money to include a time-factor, so that the SAME value in the blockchain will display as a DIFFERENT amount every nanosecond or millisencond or second or minute or hour or day or whatever.
Thus the demurrage would exist purely cosmetically in the clients, needing no representation in the blockchain whatsoever.
Done this way, the number of new coins minted per block would ALSO be perceived as being less over time UNLESS the actual number minted in the actual blockchain anticipates this and compensates for it so that on average if the blocks take the average amount of time they are supposed to then the average number of DISPLAY-COINS (as distinct from the actual number the blockchain records) comes out to whatever number it is that you are aiming for it to come out as.
Not sure I understand this part.
Basically "the unwashed masses" need not ever concern themselves with the mysterious fact that the numbers in the blockchain do not change yet the number of DISPLAY-COINS, which is the actual number used in real life, being the actual number taking into account that moment in time's demurrage of the entire all coins ever to be minted including those not minted yet, changes constantly.
Yes, but again, not sure what you mean in the bold part.
Basically even block explorers would display the display-amount based on the moment the block is explored, only highly technical machine-code-types needing to know the obscure fact that the blockchain uses constants to express amounts that in reality are changing moment by moment.