Hi,
I am pretty confident that the ‘Amp_r_n’ corresponds to ‘Speaker -’ and ‘amp_r_p’ to ‘Speaker +’.
If you have a multi-meter you can check the jack inlet and the last two rings should have continuity with the ‘AMP-R-N’ and ‘AMP-R-P’
All the other terminals is pretty much the same but they labelled them slightly different. I would check is the cable itself is good as due to rupture it can be broken inside the insulation and that is why you get interference in the ear and no mic.
I would get a brand new 4 core wire if I were you to eliminate this issue. Get 4 core shielded so the mic has the least interference possible.