1st of all - about vocalz. I 4got 2 say:
ALL vocals & speechez r in RUSSIAN !!!
Thus you probably COULDN'T understand it @ all! ( The probability that you can speak russian is a little %) )
Main vocal also DID NOT sing - it wasn't planned 2 make vocal line of notez - but growl instead. But growling was also rejected - 'cause i found impossible 2 make text understandable @ THIS TEMPO!!!

I had recorded 4(FOUR!) growl-vocalistz but nobody of them can articulate words of text @ this tempo so that it can be understandable for people, previously didnt listen this song!

So ... i was disappointed but didnt wanna give up the idea. So i recorded another vocalist - from PUNK group instead of true-serious metal !!!

Only after this pervertive change of art toolz i've reached the aim - the text of song became understandable !!!
Left & right guitar was recorded with some different mic to combo positions - so it hard to figure how to compare the loudness of both. Sometimez i think left guitar louder, sometimez - rite )).
For plastic sound - is this about absence of sound @ freqz more than 10 khz ? Or what did u mean?
On limiting: i limited this just to reach standard level RMS -9dB. Not more. I ve been tuning limiter release, attack(more xactly - in my limiter there is look-ahead or "pre-tune" instead of attack) and treshold tp get sound @ needed RMS while not unpleasantly distorted. So - if somewho can advise limiter that can do this task better (or does it quite well on your earz) - please tell me !!!