You just have to buy the game legally, then patch. Suggesting anything otherwise will make your tenure on this forum very brief. 
(Although it’s entirely possible I misunderstood what you were suggesting…)
- Download the patch from the mirrormoon website, and run it - it will guide you through the installation process. (It will tell you to insert the game DVD when needed).
- Doesn’t matter
- Right click (or 2 right clicks if you set it up that way), to access the in-game options, click on the save option, and choose a save file slot.
- Same as 3, except choose exit game.
What’s the drive letter of your DVD drive?
You could try installing the game first (in Japanese) and then the patch. The installer has been designed to work both ways.
Could the error be because of region encoding?
The standard for data DVDs does not define region encoding; in short, data discs cannot be region encoded. Region encoding only exists on the DVD-Video (and possibly DVD-Audio) standards.
EDIT: Or do you mean nonunicode charset encoding? In which case, I don’t think so; both mirror moon’s installer and patch are designed to work just fine with Latin-1, and the poster already showed that (s)he was using the SHIFT-JIS nonunicode charset before.
- Alt+F4 works as well.
As for the problem, Japanese settings? Are your regional settings all set to ‘Japanese’?
$118? Wow. That’s including the postage fees, right? OTOH, at the current rate, ¬•9240 is $87 because of the cheap dollar, so that’s not too much of a rip off. 
Bad times for US people to buy erogames.
Glad to hear you’re enjoying it. I thought it was worth the hefty price tag too. 8)