Sorry no, just no. He'll be ok in a 75. I've seen plenty of people on here with a rd in 75 and they're fine. Hes an f1 RD and not a midas. I doubt he'll reach the 12 or 13 inch mark, maybe 11. I had questions about him digging all the time, not tank size. If I wanted to be berated about tank size, I'd go to petsmart and ask for a pleco and tell them I'm putting him in a 10 gallon.
Red Devils actually get longer than Midas. Midas cichlids are just taller and thicker