i think i nailed the quality i was targeting when i started this all principled glsl, my pretention was never to supplant blender eevee or principled shader, but simply reach a good level of quality to fake path-tracing-pbr-ish like render in real time with my very low entry laptop, they said solutions come from adversity, i definitly confirm.
i put the challenge further and try to render the scene at 10k.i had to made some concession, but here it is: