would this self extraction cap help to keep the bolt in place?
Only after it was already too loose to hold the crank in place.
If your crank is still loosening after you've reassembled it correctly (proper lube, proper torque), the damage is already done and it's new crank time.
Regarding my problem of the crank bolt loosening repeatedly two pages ago, would this self extraction cap help to keep the bolt in place?
https://www.bike-components.de/de/FSA/Kurbelschrauben-QR-1-p7630/
Or maybe even Ti for extra pimpness
https://www.aliexpress.com/item/32626686582.html