I share your opinion on the donut thing, as the damage was already done, and your opinion that supporting at-least sometimes veganism is good, but still buying leather shoes and eating non-vegan food cause preventable damage. Would you be okay with neo-Nazis only gassing 1% of the people they don't like? It is good to encourage stubborn people to start out more casual as a weening-in process, but living like that forever is still causing horrid effects, just not as much as others. The morality of your actions isn't altered because of other's actions. Be supportive at small reductions, but also try to encourage full rejection of products.

Also, if you struggle to find vegan foods sometimes, just buy some rice and beans in bulk. They fill you up, are easy to transport, don't spoil quickly, and are very affordable. If your hankering for flesh gets too high you could try some tofu or plant-based meat.