Aphids, generally, are attracted to plants wiht lush green growth, many research sources say because of too much soil Nitrogen. The simplest short term means of control is with a sharp blast of water that knocks them off the plants. Long term control is to be sure the soil is good and healhty with balanced nutrients.
Whether the Bacillus thuringiensis will harm the butterflies you want around or not will depend on which one you use as well as which plants it gets sprayed on. Judicious use will protect those you want around.
Slugs like the environment that organic gardeners make, cool and moist with lots of decaying organic matter (mulches) as do many other wee insects. Floating row covers can help with several insect pests. Judicious use of any pesticde is always the best use of them and companion planting can help as can a garden of wild flowers that will help attract the beneficials that predate the insect pests.
However, the single best way of pest and disease control is to be sure the soil is a good healthy soil that will grow strong and healthy plants.

Here is a link that might be useful: Cucumber beetle

Sunny, your list is all organic, rest assured. I'm glad that you've given the Bt some careful consideration,as it is being used much too freely in recent years. But if you have a large area of a favorite host plant to protect, don't hesitate to use it, as a last resort.

I don't use DE in the outside garden areas, anymore. I can't justify it's broad spectrum use. But I still keep it around for our garage, where black widow spiders have been known to proliferate. Yikes!

I'd add neem oil to your arsenal, as well as a horticultural oil of some sort. Both are extremely useful for a wide variety of problems (including some diseases). I have also begun using a product called 'Surround'. It's a kaolin clay suspension, which sprayed on susceptible plants, discourages chewing pests and others. I originally got it for the Japanese beetles (works great), but have since used it on other plants. It also protects against heat!

Thanks for your suggestions and confirmation that I'm in fact doing organic gardening. I have been trying hard to watch out for the beneficials and control only the pests.

I just purchased some BT and Neem oil yesterday. I plan on using the BT in limited areas like on the corn. I'll keep the other suggestions that you've provided in mind too.

Thanks again!!