Then when the accelerator makes the return journey, Earths clock runs slow until the two are in perfect sync when the accelerator reaches Earth but then the Earth clock jumps forward another 302 years when the accelerator accelerates back into Earth's frame?
It makes no difference in this case if you are travelling away from or towards the Earth.
If the rocket had left at the beginning of the year 2000, it would arrive at the planet in 2528.57 (528.57 years later) according to Earth, but because moving clocks (relative to Earth in this case) slow down, the spacecraft clock would read the planet arrival date of 2377.47 (377.47 years later). If the rocket decided to return home after 2 years, then Earth would see it arrive back in 3059.14 (2 + 528.57 years later), but because moving clocks (relative to Earth in this case) slow down, the spacecraft clock would read 2756.94 (2 + 377.47 years later). This means the spacecraft would have aged 302.2 years less than if it had not gone on this round trip.