So this was a fun premise and good execution, but I hate the reasoning. The original time or at least the first one we know about, Barry Allen had his parents, became the Flash, is a hero, got a fanboy (in the future which means the future is safe from the wonder woman and aquaman war) who became a villain. Second timeline villain goes back in time and kills Barry's mom, frames his dad so he doesn't have his parents, he becomes the Flash, is a hero, fights villain. Third time line he goes back in time and saves his mom and that mess up everything ever to the point that the city or world is off point so Kal-El's pod hits a city instead of farm. His mom dying was not integral to Barry Allen becoming the Flash the first time what stops the third time line Allen from gaining powers? Based on the fact that changing things to the second time line's history to make it mirror the first time line's history ended up with a vastly different third time line how would Barry Allen going back and making things mirror the second timeline fix anything instead of creating a fourth time line potentially worse?
No matter what Barry does the time line will be different and the world as he knows it is dead. I'll keep reading this, but he could have changed anything other than his mother's murder as it is not some key point in the universes history or it would have mattered to the first timeline. He could have given Thawne's ancestors a vasectomy. He could have gone way back and kicked a stranger for all he knows. He doesn't know how and doesn't have the control to change things as he wants so why the bloody hell would he pick letting his mom get murdered?