I'm getting core overheating and frame drops during heavy combat in Space Marine 2 with a CR-1400. Should I try an offset voltage?

When the Tyranid swarms hit, my FPS just dives from 90 down to 55, and that kind of stutter is a nightmare in a fast-paced game. The Jonsbo CR-1400 just doesn't have the surface area for high-TDP CPUs, and my temps were swinging between 85-92℃, triggering the auto-downclock. I tried 'Power Saving' mode in the BIOS, but while it dropped temps by 5℃, my 1% lows tanked to 30 FPS—not an option. I went back into the BIOS and set a CPU voltage offset of -0.05V, and pushed the fan curve to 90% once it hit 65℃. RTSS showed the frame times tightening up from a messy 18-35ms to a steady 12-16ms. The system crashed during the first load screen after undervolting, so I had to back it off to -0.03V to pass the stability check. Now temps sit at 78-84℃ and CPU-Z shows the clocks are finally stable. RAM is holding at 52-57℃.