“Is it a lack of bitachon to live within a budget, and to have (almsot) every penny figured out?”
No. While everything belongs to HaShem, we have no idea how much He will allocate to us in any particular period of time. (Unless, of course, we are prophets, and there hasn’t been one for a very long time.) Therefore, NOT to live within a budget is wasting HaShem’s precious resources.