The way this game is designed is similar to the way a few other Capcom games work, you can easily play any chapter you wish to the grind the **** out of them for gold, ammo, weapons, herbs, jewels etc, and you can just press Start and Quit, and make sure you also press Yes to save the progress which then you get to keep all the items you accumulated on that run.
Unlucky with Chapter 6-3 though. If it was Professional difficulty then ouch! You could easily unlock Unlimited Ammo by speed running Amateur though.