I have an idea, why not picking a key from the middle of 66 bit range and start adding and subtracting to it using key subtract in address mode, you never know, you might get lucky and find puzzle 66, at least this way you could adjust start and end range of addition and subtraction, then you could for example, add and subtract 1 million keys to your middle of the range key with this stride "10000000000" and then add and subtract the same to another key, repeat that until you see #66 address, but we have no tool capable of doing that by itself, so you'd have to do addition and subtraction a few million times by hand, but if we could modify key subtractor to do that by itself, it would be great.
I wonder who is a wondering developer around these woods? !!!😉