LED PWM with FOD8342 Optocoupler
This push-pull driver does not consume more than 6mA while your load is 24V+/0.3k = approx 70mA. The problem is you are not saturating the U10 driver because your input Q1 current is voltage gain is too low. as stated above.
So if the output draws current from a resistor unlike a MOSFET or IGBT AND the output voltage is not saturated, the tiny chip dissipates excessive power.
Design error
Fix the input stage common emitter to drive between the recommended range for the IR LED. I suggested 13mA which is mean of 10 to 16mA. you are lucky to get more than 3 mA less than 4 .
Test Simulation error
Then replace 180 Ohm load with a 1nF capacitor to simulate IGBT (or improved model so you do not have steady state power dissipation... just on edges.