I didn't catch all the photos in her apartment, but I do recall at least a shot of a liberated concentration camp. I think the implication is that she's been active - perhaps the year of sightings is meant to just indicate how long she's been in DC. I do think it is reasonable to assume that she's had to "reinvent" herself a number of times - you can only be an ageless demigoddess in one place for so long. Isn't she working out of the Louvre by the current timeline? I bet "Diana Prince" gets terrific references whenever she needs to switch jobs...
I don't think Barbara got two wishes - her (only) wish from the rock was just to be "more like Diana." Then on the chopper, she says she wants to be an Apex Predator - but that wasn't a "wish." However when Max is taking all the wishes from the world, he directs some of the "payment" her way, which is what transforms her into the Cheetah. I do think they left it intentionally vague as to whether she renounced the initial powerup. They could have had her say one way or the other - leaving her silent indicates they want to keep their options open,
I don't think it's much more complicated than he wanted to be successful. He just found himself in a position where he had taken a bunch of big (probably foolish) risks, that didn't pay off. And rather than admit to his situation, he tried to wish (aka cheat) his way out of trouble - but each fix came with greater and greater blowback. Surely the next wish would be the one that solved everything, right? Nope - he still needed more power, to the point where he was basically triggering nuclear armageddon. What Diana finally helped him realize was that there was no way to out game luck, and that he had to give it all back.
As for the moral, I don't think the film is saying we should just accept the world - however simply wishing for changes isn't going to make anything better on it's own either. Absolutely you can try to make yourself or the world better - just do it on your own merits, and be okay with whatever the outcome may be. Also, you shouldn't take shortcuts, whether that's in a race, business ventures, popularity, or even love. There will always be a price to pay.
Overall, I enjoyed this film a lot. Gadot and Pine were great together again, and I appreciated the role reversal from the first film. And, for personal reasons, I get why they wanted this to be a story about Diana getting a second chance with Steve, but then coming to terms with letting him go. And, the whole Invisible Jet sequence was really wonderful. I thought Pascal and Wiig did a tremendous job bringing depth to what could otherwise have been cardboard villains. I certainly feared Barbara could be another Jamie Foxx Electro, but I felt her performance was more grounded (ha ha). And man, I did not expect the climax to hinge on the conscience of a wannabe 80's oil tycoon - but Pedro pulled it off.