Reading thread in general, I know you're running a i5 but, my i9-13900KS
really likes low SA voltage. It's quite possible that all this time you were butting heads with your system, you were having crashes because your SA was set to a stratospheric 1.35... are you still using that much voltage? I'm on DDR5, but for 6400 CL30 it was enough to use just 1.1 V for SA. At more relaxed timings, SA voltage actually needs to decrease, at CL34 from my XMP kit the sweet spot is around 0.9. More or less lead to crashes in both cases
Honestly at the point you are, further gains from tweaking your memory any further would be academic at best. Only tightening your secondaries and tertiaries to perfection you would see any meaningful difference in benchmarks, you're not going to see any real world improvements from there on out, DDR5 may help you eke out a little more but, at that point you're looking at a new motherboard and a new memory kit. Just enjoy your rig for what it is, man.