Ultimately, like I said, it’s up to you, but it is piracy. If they release the OOT officially are you going to download that illegally too? Same logic.
As said, I haven’t ever seen the original soundtracks for sale anywhere. I’ll look into it but I don’t think they’re actually available outside non official retailers, meaning they fall into the same category for sharing copies as the DSEs do. This site well knows the grey area it falls into and I think this is where the OOT soundtracks now fall into as well. I will see if I can confirm that though before proceeding further in obtaining them via other means.
No, this isn’t accurate. They’re readily and officially available on vinyl and digital (not just iTunes, but also places where you can get them at higher bitrates). The analogy to the OOT would be if Lucasfilm officially released them on Blu-ray and digital, and you justified pirating them because there wasn’t a DVD release.