Should I be leaving my job with hectic working conditions (above median wage), if I've cash buffers of >5 years (including mortgage), to take a break (recharge and harness future ready skills) in this current climate?

Seems you are well prepared, go ahead! If you find yourself getting a burnt out, is good to recalibrate however you might want to ask yourself what if the next job also has hectic work hours, will you quit again? In life, its best to strike a balance but for now it seems you really need the break so go ahead mate!

Yes, go for it but make sure you have money to survive for at least 1-2 years because as you already knew, it's a challenge to find job during this crisis. Once you leave your job, you may find a hard time to find another job if you need money. Thus think twice before leaving your current job. Good luck!