The Speed Force and the Metagene are related to Magic: The Gathering's Planeswalker Spark.See Magic: The Gathering for details.
The speedsters created the Speed Force, not the other way around.Those with the proper Metagenes pooled their powers into a single extradimensional space, causing it to become increasingly sentient and influential. Their speed comes from themselves and flows into the Speed Force. The original energy comes from the same source as all the other energy-generating metahumans. Possibly The Source is the source.
Alternatively both the speedsters powers created the Speed Force just as simultaneously the Speed Force gave them their own powersGiven that the Speed Force permits Time Travel, this would be a Stable Time Loop.
That place Mirror Master goes when he jumps through a mirror is Despair's realm from The Sandman.Despair's realm is "The World Behind the Mirrors". How could it not be the same place? As to why they've never met — notice how we never see the bottom of it in the Flash comics. Despair always hangs around on the floor.
All speedsters in every universe gain their power from the Speed ForceFlash, Quicksilver, Sonic the Hedgehog, Synapse, Superman, even the fastest Transformers and race car drivers gain their affinity with speed from it. Alternately, the above theory that speedsters create the Speed Force could also be true in this way.
The Darker and Edgier story about Barry's parents is, in canon, a continuity burp.Consider these following points:
The new Barry Allen will be a villainThis follows naturally from the above guess. We've got two other Flashes for heroics, so...
Flash can fly.Theoretically, there no reason he can't; he can violate every other law of motion, inertia, and gravity at will. Johnny and Jesse Quick, who also tap the Speed Force, can fly. DC's version of Mercury/Hermes, God of Speed, can also fly, and those who gain "the speed of Mercury" such as Wonder Woman and Captain Marvel also gain flight. The Kingdom Come Future!Flash can fly.
Parallax is now able to tap into the Speed Force.At one point in Brightest Day, Parallax was able to combine Barry Allen's speedster powers with his own Reality Warper fear-mongering abilities through possession. Once a speedster touches the Speed Force, (at least presumably) they can tap into it again. Thus, Parallax, via his short stint with the Flash, has acquired superspeed.
In another universe Jay Garrick is FLASH! AHH!AHH!...and Hawkman is one of the hawk people. Queen.
The Speed force is Barry's StandIt's fueled by the power of Barry's life energy, though it lacks even a rudimentary-humanoid form. So Stand-like, but not exactly a Stand.
Wally is still Kid Flashto Jay Garrick on Earth-2.
The various changes to the Status Quo are because Barry didn't know every detail or think to add them in.Barry actually had to recreate the DCU from scratch when he reset everything during Flashpoint, but as he's not perfect or godlike, he didn't remember every detail perfectly, or because he chose to change them under the belief he was making things better. These include: Superheroes now wear armoured looking suits, because Barry wanted to ensure they would all be safer. Barbara Gordon can walk again because Barry hasn't met either of the successive Batgirls, and as such didn't add them in. The age of heroes is only five years because, thanks to being gone for so long, Barry only knew about fie years worth of info about the world. He tried to put in what he knew and what he was told, but thanks to his gap time, he could only fit in so much. Iris is gone because Barry was thinking that, without him, she would have a safer life away from super heroes. He didn't realize that this would also remove the reason for him knowing Wally, resulting in Wally never becoming Kid Flash. His time as Flash is gone as well because Barry wasn't present for that. A number of characters, specifically female ones such as Sarfire, Harley, and Amanda Weller, who were sporting more sexualized designs is because Barry is a Covert Pervert. ...But the ones were are less sexualized are because he's not an outright pervert and wanted to give them more respect. ...nd he changes to Blue Beetle are because, as great a guy as Barry is, he's uninentionally a litle racist against Hispanics.
Continuing from above, this will be the setup for Batman, Titans, Flash, and others to team up for a miniseries to bring back some of the missing characters and fix the more controversial changesIt will start with Tim Drake, Red Robin, realizing that he feels like there's some people missing; he vaguely remembers Cassandra Cain and Stephanie Brown, Batgirls 2 and 3/Black Bat and Spoiler, but can't name or picture them. Until, when talking to some other heroes, he remembers them more clearly, and begins trying to investigate this. He discovers some other details he vaguely remembers, coming to him in dreams, and ends up tracing them back to events that had Barry Allen involved. He confronts him wih this, and together hey find out what Barry did and, teaming up with Bruce Wayne/Batman, Dick Grayson/Nightwing, and Kid Flash/Bart Allen, they try to find out where the mising heroes are. Meanwhile, on another world created by this event, Cass, Steph, and Wally are kept prisoner by some evil force, along with the other missing heroes. Together, the three manage to free the others and try to find a way home. Only problem is, they all have no memory of their previous lives. Eventually, both Barry and Wally are able to remember each other when they boh connect with the Speedforce, and comunicate. Wally is at first shocked to discover his uncle forgot about his existence, but quickly forgives him when Barry realizes his mistake and feels deeply guilty. Together, they go on to fix some of the damages together, resulting in reuniting Steph, Cass, and the Bat Fam, as well as returning Wally and every other hero to the universe.
The new Reverse-Flash will be Wally WestHe will still have memories from his pre Flash Point and New Fifty Two days. And wants revenge against Berry for erasing his entire family, related and extended, from the timeline.
The Black Flash was working for Nekron.Those on top of Nekron's hit list are those that escape death. The whole point of the Black Flash is that it prevents speedsters from escaping death by outrunning it-the Black Flash is a servant of Nekron created to hunt them down. He let the Black Flash exit during Final Crisis to deal with Darkseid, and the Black Flash died afterwards because Nekron had set things up to solve the problem of life once and for all.
The new Reverse-Flash is Daniel West, Iris's brother.He was one of Barry's first arrests as the Flash (and he contained Daniel again as Barry shortly after), Reverse-Flash only started to appear after Daniel was released and arrived at Central City, and he attacked everyone who entered the Speed Force — except Iris.