I newly tried memtest, freshly download from the site, and ram is fine (still @1600mhz). (the other memtest i had was one included in a linux mint live iso and freezes at the beginning of the second test)
I placed a 140mm fan on the side of the case, it covers the entire cpu + ram area, and maintained the 120mm intake on the front.
(not beautiful, but working!)
May i'll look for a 90mm for exhaust on the back.
About 10c drop on the cpu, but it was already good.
I noticed last time, my MB was damn hot.. so i hope now it runs cooler.
stress test with y-cruncher on a live manjaro
(lol, i noticed i took the screenshot the only moment cpu wasn't @100% load)
Now, finger crossed and hope it gonna works.
Thanks for the advice guys