Correct on the first two, the third was Ayla Ranzz (Lightning Lass), crossdressing in the early sixties…
Reserving 1 DQ.
IQ1: Were you a scientific collaborator with Brainiac 5?
IQ2: Did you appear in an early JLA/JSA crossover as an antagonist?
IQ3: Did you find your girlfriend’s corpse in your refrigerator?
1 was Rond Vidar
Your answers for 2 and 3 are correct enough (though I was thinking of Power Ring on 2 for the trio of Green Lanterns, and I think 3’s last name was actually Rayner)
DQ: Died after 1964?
DQ: Best known for contributions to the Arts, performing or creative?
IQ1: Did you famously refuse to change seats?
IQ2: Were you one of the group of four Legionnaires kidnapped and memory-wiped by Universo?
IQ3: Were you a Soviet member of the Justice League?
IQ1: Did Madonna sing about you in “Vogue”?
IQ2: Was it revealed at one point that you would become the Time Trapper?
IQ3: Are you half of the original Firestorm?
IQ1: Did you write a Graustarkian romance called The Mad King?
IQ2: Were you the protagonist of a Graustarkian romance and its sequel?
IQ3: Did four men ask whatever happened to you?