do you have to use cream cheese as the frosting? If you can't buy any, then I would just make another type with what you have available. Also- does the cake have to have 80 flowers? Can't it be less and just redesign the cake to something more manageable? Honestly that is what I would do...try to make it as simple as possible because you do sound very stressed.
edited; sorry i see that you're not using the cream cheese anyway. Just use a bit less butter in your SMBC (to taste less buttery) and maybe add some shortening in there (with the butter) for heat stability.