Thank you another book/trilogy to add to the reading list.

I don't think a gold standard is a viable pyramid scheme for a multiplanetary species. There's too much of it in space. You need something that is rare even after traveling for hundreds of years. A lot of wars were simply fought over resources. It's even better if your society uses the resource as money. The only thing I can imagine is using habitable planets as currency, this would require your galactic empire to have a dozen planets though because a single planet does not make a currency and the debt trap of borrowing 1 planet at 3% interest would fall apart because colonizing the next planet may take too long to pay off the interest. I.e. you need some planets to lose before you take that loan.

Edit: Great filter hypothesis to explain Fermis paradox. The pyramid scheme needed to enslave the galaxy is also powerful enough to destroy a planet before it develops space faring technology.

Yes but that is only if you are traveling through space faster than light. If you simply skip some of the distance with something like an Alcubierre drive there is no time dilation to deal with.

But, it doesn't enable time travel. It just makes calculation easier, like «bending» of space-time array.

If you switch from relativity to regular physics with medium instead of pure vacuum (10 years passed since 2012 already, so relativity is busted at this point), then c is the speed of light in medium, so we don't need to bend anything or use negative t to calculate outcomes.