1. I can install Impulse, download whatever product(s) I purchase,
transfer them per USB to my Offline computer and use them there?
No. Impulse will have to connect one time on the off-line computer.
[Sub-question] How do I activate said products without an Internet connection?
Once Impulse is activated all you need is in the Impulse-archived file.
2. Having then downloaded what I need, I can uninstall Impulse and still use my products?
3. Does Impulse uninstall cleanly, or does one need to manually sweep the registry looking for leftovers?
I believe some reg keys are left behind.
Stardock is workin on a system to allow for totally off-line activation. Because Impulse is a storefront and digital download system for other developer's app this has to be secure enough for them to feel comfortable with. It takes time.