If the petunias were blooming well, why worry about aphids? One pot with a few plants is not much to rely on if one wants to attract any kind of wildlife. If you have the discipline to change the sugar water daily, a hummingbird feeder is an ideal way to get a good look at hummers. I have hundreds of various nectar-producing blooms in my yard on a given day during the warm part of the year but hummers go to the feeders much more often than any Lantana, milkweed, Salvia, or other single type of nectar plant. I am not saying don't put nectar plants in your yard, but relying on a few snapdragons in a pot for the sole purpose of attracting hummers may not be as rewarding as you hope. Having a few snapdragons in a pot because you love them and hope you might see a hummer visiting them is a great idea.

National Audubon Society has published this warning about using neem oil outside on blooming plants:

* A note on the use of neem oil, which is an insect growth inhibitor and non-toxic to birds. Because neem oil prevents insects from developing further, it can prevent bee larvae from developing if adult bees feed them neem oil-coated pollen they've brought back to the hive. For that reason, you should avoid using neem oil on flowers or remove open flowers from plants you're treating with neem oil.

https://www.audubon.org/news/bird-friendly-plants-faq (Question 20)

There are pics of hummers visiting marigolds, I don't know why they would be repelled?