One option might be to treat underground rocks like surface rocks where instead of finding a tiny amount of iron you have a chance to find a tiny amount of the minerals in surface rocks.
Perhaps change the distribution of veins too? Instead of an iron vain containing just iron, make it 80% of...
Get creative! Take the metabolism perks, sexual t-rex, miner 69'er are all great at reducing your food/water needs. Find a trader or POI with a forge and every 10 sand and 1 clay soil is enough to make 5 jars. You can have a week's supply in just a few minutes. In non-desert biomes the gray...