Well, there are a lot of mixing here. Don't confuse PS3 region, with signal coding, with DVD region, with BluRay region. Those are unrelated.
- PS3 region means locking up games to certain parts of the world (based on the numbering pattern used by Sony: 00 Japan, 01 USA, etc.) in order to avoid game importing and use of software only on certain regions. The PS3 was mostly unlocked for games and other software (except for a few games locked to Japan), but 99.9% of the PS3 games run in every PS3 (as it should be). That's why you can use most of your digital content on every PS3 you own.
- Signal coding is a signal transmition coding standard used to process and display video on different devices (TVs, cameras, videotapes, video players and recorders). Each country adopted certain norm (PAL, NTSC or SECAM) based on these definitions:
- DVD region was the first true locking system that prevented DVDs to work in every region. The region was "chosen" on the player and couldn't be changed. Then the PC DVD drives came and Windows allowed to change the region 5 times, after which the last region chosen was the one used forever. But all of this changed which piracy and hackers, developing tools to avoid the checks and new players without region lock, rendering the entire locking system useless.
- BluRay region is the same as DVD, but most player manufacturers opted to allow to play any region discs on their hardware, making the locking system useless.
Bear in mind that DVD and BluRay regions are pointed towards the market of each specific region, so movie studios have control on their contents and distribution. For example, Japanese DVDs and BluRays will have content for Japan: subtitles, audio tracks, bonus contents, etc., and removing anything that doesn't comply with Japanese laws (a.k.a. censorship).
Nothing to worry about. Sony lowered the maximum limit of PS3s activated consoles on a single PSN account from 5 to 2 (this happened almost 5 years ago, if I remember correctly), so you are on the limit and no other system could be attached to your account until another is dettached from it.