For rearing little hatchling dragons I use the same 100L converted tubs I used to rear my two bluetongues until they were about 12months old and grew too big for a tank 45cm wide x 80cm long.
This is the set up I used for my rearing tubs :
https://www.beardeddragon.org/forums/vi ... 4&t=233480 I've reared two baby / juvenile Eastern BTs in these, then 2 pairs of central bearded dragons from hatchling to 15 months old , and currently have Fluffy an adult water skink in one.
Your little BT will be fine in a 75Gal …. lots of space to explore , only real issue will be live fast moving insects like crickets , roaches and locusts will more easily get away and hide in 75Gal than they can in smaller foot print rearing tank or tub.