If 1.8 sponge both sides is heavy to you... then the viable options you got are... (but you will not like most of your options)
- lighter blades, WAY lighter blades like 70 grams, but you like your current blade and a feather light blade will feel way different
- OX rubbers, but you like sponge rubbers
- LP in OX or thin sponge, but you do not want to be a material player
- Play on the space station, everything there is light, but no gravity make TT no fun
- a tourniquet to the neck will stop all bleeding, but you are not bleeding
- gym membership and TT training with lots of match play seem to be the only logical direction remaining
If you were to take an extended vacation to Japan, Korea, or China and play daily for hours in a club there with multiball lessons given by a former pro who will train you with the sole objective of running you ragged until you drop, after a month or two you will no longer think your setup is problematic heavy.
To me, I will not play with a setup under mid 180s grams, even that feels light, but if center of balance is low enough, I can play with that bt. My preferred weight range of bats is 200-210 grams total with low or neutral balance including grip and edge tape.
You could try to eat lots of spinach, but that only seems to work well for Popeye the Sailor Man.
Serious, I do not see how a bat with 1.8 sponge can be heavy, unless the blade is made from an anvil. Such a setup ought to be under 170 grams easily, unless the blade is extra oversized.