I’ll do 2 on one off and every 3 weeks change up the routine at least slightly, that’s correct right?
Correct.
Also a general question, given my starting measurements, is 8x7 a realistic goal overall or it’s too much to hope for in your experience in this community?
Your current objective, not really a goal since your goal may be 9x7.5 in the future, is very realistic from 5.9x5. You have a head start ahead of me. Mine was 5.25x4.25 way back when, and achieved ~7.2x6.3 in around 2.5 years on a very slow, safe and steady pace. I still want to resume to get 9x6.3, or even 9x6.5 (with possibly a bat to my head because of the girth). So yes, you can indeed get your 8x7.