Can I debug my iOS app on a device without adding it to the Apple provisioning portal?

Question 1

No. You need to be running on a device that is enabled for development. This will need to have been added to your development portal.

An enterprise-signed app won't even allow a debug connection.

You can run it in the simulator and attach to that without a provisioning profile however.

Question 2

It's now free with Xcode 7 (beta): https://developer.apple.com/xcode/

Now everyone can get their app on their Apple device. Xcode 7 and Swift now make it easier for everyone to build apps and run them directly on their Apple devices. Simply sign in with your Apple ID, and turn your idea into an app that you can touch on your iPad, iPhone, or Apple Watch. Download Xcode 7 beta and try it yourself today. Program membership is not required.

Question 3

General advice

You must bend your development style to match Apple's requirements. If you plan to release to the AppStore, you shouldn't spend an extraordinary amount of effort bending Apple's system to your desires.

Enterprise account

Enterprise accounts can be very useful for basic UI testing, and if you have good crash and regular debug logging through a service like Hockey and CocoaLumberjack you can actually do quite a lot of testing without needing to provision each device. Remember direct (USB) debugging with your Enterprise app is disallowed.

Jailbroken device

If you have a jailbroken device you can load apps and change the entitlements of the app to run. To change the entitlements arbitrarily I use tools like Saurik's ldid which I've made easier to compile using CMake.

Entitlements

The hardest part with repackaging apps to load them is dealing with entitlements. While some things can be bypassed, network-oriented entitlements like APNS, iCloud and Siri become much more difficult to hack out without loss of functionality.