1. Stardock currently is using two methods to download software: The first, for people with current subscriptions is through Impulse (the download and update platform sold recently to GameStop). The second is through the "Store" located here: https://store.stardock.com/login.aspx
Login is with the email from which you bought your subscription. Your password is what it is.
These two methods will be replaced with a "simple, unobtrusive download app" in the future, date uncertain.
As long as you download and archive both your software and installer, you should have no problems restoring things. I'd also suggest saving these things on an external drive. Also, if you clone your drive to the external, you should avoid all problems.
I'd suggest putting a "tickler" on your calendar to make sure you download and archive the latest stable update to your software before your subscription times out (if you're not planning on renewing). You are entitled to all updates between major version changes during that year. Generally, though. Stardock is generous in interpreting that. Say they update to WB8 within a few months of your purchase... they won't stick you for an additional fee for the upgrade. That's just my experience, though. I am not a Stardock employee nor do I represent Stardock.
2. Eventually, yes. I doubt it'll be anytime soon, though. Again, refer to my thoughts in 1.