You technically cannot kill souls. Souls are immortal. There is a difference between plant life and animal life, though both have souls. Plants do not posses sense organs that registers emotions, pains, suffering, happiness, desires etc.. But animals are higher than plants and posses sense organs that registers emotions, pains, suffering, happiness, desires etc.. Your position is also valid because total liberation is not possible until you give up this body! But you want to live this life minimizing sins. There is a fine law of nature that governs existence. A tiger kills deer when he his hungry. This killing by tiger is not consider as violence or sinful act based on cosmic constitution. The tiger body is not equipped with human intelligence. Humans are responsible for their choices because they possess intelligence. Fruits, vegetables can be consumed for the protection of your body. Self-protection is your Dharma but self-protection on the expense of other living entities who feels emotions is a sinful act.