For those interested, check out the new Idle Master FAQs.
This generally covers the questions I get asked most often. I'll try to keep this FAQ list updated with anything that comes up, and I'll be putting an auto-responder on my email account that points here and to the ES FAQ page.
Buying DLC also earns you card drops in F2P games, and last I checked the amount of drops you earn is based on the base price of the DLC rather than what you paid, which I assume is to cover retail key activations. I haven't idled since circa the release of Styx, though, so I'd advise contacting Valve and ensuring the details are correct before updating the FAQ.