Rome nor any city was built in a day...the same is true for this challenge.
It's critical to understand that, and that you just have to come up with your own way of approaching this challenge...1 piece at a time, regardless of how large or small that piece is.
So I ran a smaller card, GTX 1660Ti, for 8 hours in the 66 through 69 bit range, searching for the addresses of #66 through #69 challenges.
In those 8 hours, the card generated 14,690,305 different starting keys/points and checked 2^20 keys from each starting key/point. I saved every random starting point and added FFFFF to each one to show the ranges and keys checked in those 8 hours.
That is only 15+ trillion keys checked in total, but they are all spread out over the 66-69 bit range.
If you want to look at what this single card was able to accomplish in 8 hours, you can download the text file here and look at all the different ranges searched.
The file has been sorted for easier viewing.
link:
https://easyupload.io/tyeppzpassword:
BTCChallenge
Let me know if you have any issues trying to download the text file. The file is only downloadable for 7 days.
One piece at a time...
(I am running round 2 of the same setup; a single card, searching for the four addresses, 66 through 69 bit. I will upload that file when it is done running/I stop the program.)