I haven't seen the original, but this could easily pass off as the real deal. From your descriptions of the flaws of the original material you were working with, this lives up to being a completely transformed product. Some over the top action sequences and one-liners were sprinkled throughout, but they ended up feeling like a nice break from the much more serious tone of the film rather than being tedious. The actions sequences felt just long enough, and many of the featured fights still looked great on their own. The characters of Batman, Joker, and Superman feel very consistent throughout. Highly recommend anyone with even a passing interest in Batman to give this a go.
Having never seen the original I cannot speak for any changes made, but their presence is invisible and nothing at any point appears to be missing.
While not my favourite Batman story (albeit with minimal knowledge of the comics) it is definitely a worthwhile entry in the canon, and I can certainly see the influence that this story had on following works involving the character, Thanks Blueyoda for assembling this project!
By far the definitive version of TDKR movies. The only small gripe is the "NO MORE" line from Batman fighting Joker is still in the fanedit, but for the most part, it removes every one of the superfluous flaws from the movies that I had problems with. Highly recommend this fanedit, and this will be my go-to from now on.