Is pushing my Macbook to limits is harmful?

No, because the fan is running at mid speed. Even if the fan was running at high speed, the temperature would still remain about that anyway. If the cooling system is unable to maintain temperatures, then the CPU will become throttled so that the cooling system can get things under control again. With recent Intel Macs, almost anything will cause the CPU temps to spike to near 100C, of course the more activity the longer the temps will remain high until the fan(s) kick in and may lower the temps to 65C or 80C. Just use the laptop for whatever workloads you wish.

Hi,

I think it's not harmful, though you would use laptop cooler.