Why is better between explore the dungeon entirely so that find a maximum of items, gold and experience, or explore partially so that not to consume too food (and starve ) ?
Fully exploring each level is probably the safest option. Food shouldn't be a big problem, even in the beginning. Stock up on rations before you go on an expedition, and try to keep exploring at a steady pace (clearing new areas will yield more food). You might also try to place a race or class with the
Food Preservation skill (eg. drakeling or ranger)
And subsidiary question : Is there a means of break the locked doors from a far in order to avoid the traps ? I tested magic (fire bolt) and this seem to be not working.
You can throw anvils or huge rocks (the ones that weigh 1000s) to break doors from a distance. They are a hassle to carry around for most characters, though. Also, be sure to join the thieves' guild to learn the trap detection skill.
As always,
Minotauros