I agree with you, this game really is much harder than the original. All I can recommend really is just going in, fighting a few battles, then leaving to heal up, then do it again. I know thats sort of a crappy suggestion, but I can't really think of many places which give really good experience that you could actually survive in up to that point. By the way, if you were thinking of playing FFIV through again, and you chose the DS version over the original or the GBA version, then shame on you. Everything about the DS version has been made worse. The stupid augments, Cecil's very useless Shadow ability, the cutscenes are extremely cheesy (especially when he takes the Bomb Ring to Mist and then is like 'What have I done? NOOOOOOO!'), Edward (but he was always useless in all fairness, just a bit worse now.) And of course its biggest let down: the re-done music sounds terrible, especially through DS speakers. I recommend you start this game again on the GBA. Now there's a good suggestion for you

Hope I helped!