According to Theravada, the Buddha allowed his monks to eat pork, chicken and fish if the monk was aware that the animal was not killed on their behalf.
Not necessarily. The Buddha was not a vegetarian. He did not teach his disciples to be vegetarians and even today, there are many good Buddhists who are not vegetarians
It is true that when you eat meat, you are indirectly and partially responsible for killing a creature but the same is true when you eat vegetables. The farmer has to spray his crop with insecticides and poisons so that the vegetables arrive on your dinner plates without holes in them. And once again, animals have been killed to provide the leather for your belt or handbag, oil for the soap you use and a thousand other products as well. It is impossible to live without, in some way, being indirectly responsible for the death of some other beings, and this is just another example of the First Noble Truth, ordinary existence is suffering and unsatisfactory. When you take the First Precept, you try to avoid being directly responsible for killing beings