It's good if something now is better.
I think your CPU temperature is quite high while your fans is'nt running that fast. I wonder why your fans is'nt running faster at this CPU temperature, especially if you have no power saving on, and run high performance settings.
- Have you checked your Fan control settings?
- Have you tried to run the Apple Diagnostics tool to check the hardware to see if there is an error and to locate the error? I think it also repair some issues. I'm not sure. but perhaps it's a good idea to make a backup of your files before running this.
- Have you checked for dust and such?
You say you don't have issues with mainstage. Do you know how CPU demanding that is? Does it reqire as much CPU as AL3 does when running he MULTI presets you use? (Keep in mind that not all Multis have the same load on the CPU. Perhaps you can run some.)
Also keep in mind, that many audio applications either put full load on one CPU core or more load on one core that on another. In that case, then you perhaps can spread the load using more instances.
You can check the load you have on each CPU core.
You can try to run a soundcard buffer at 512 samples, and if needed perhaps a samplerate at 44100 Hz. Does that make a difference, and can you work with this settings?
About the score you mention, then i have found this:
https://browser.geekbench.com/mac-benchmarksWhat does your singlecore readings say? Perhaps the score around 3000 is'nt that wrong? Which model, year, CPU?) Are you sure your reading is'nt a singlecore reading? If not, then you might have a hardware issue, and need a technician to tell, if that's worth it. But if it's a singlecore read, then you might have the power to exspect.
If i understand you correct, then you only (or perhaps mostly?) have issues with MULTI presets (2 layer?) now? If so, then that's perhaps what to exspect from your MAC with the settings you have, and then you can only do what's possible to maximaize your MACs performance and to put less load on your CPU. Or you need more CPU power, too do what you wan't to do. The above mentioned tests and checks might help to find out.