For what it's worth, using my variant of ATTinyCore ( optiboot/README.md at master · sleemanj/optiboot · GitHub ), I can compile your sketch above for the Tiny85 resulting in 6556 Bytes of flash usage (and 379 bytes of ram).
Not tested, just compiled, I don't have the leds or whatever to test with.
Because FastLED makes some assumptions about the core, the following needed to be added to your sketch (at the top is fine)
extern "C" {
volatile unsigned long timer0_millis = 0; // FAKE FAKE FAKE!
}
because the ATTinyCore (and derived) don't use this variable name to track their millis, the only reason I saw that FastLED wants to access this is to "correct" millis counts when it is taking longer to operate and causing missed interrupts, so if you don't really care about millis accuracy it might be OK (might).
Also the aforementioned yield() problem, which I just commented out the call to (FastLED.cpp line 132)