Go ahead hone unarmed combat skills till useful, you will starve to death long before you are a threat. Know how yo use a gun, absolutely know how to purify water xnd grow food or long term you are dead anyways.
Dedicated martial arts takes 4+ hours a day to maintain. That is impossible for most now let alone post shft, add to that most of us are older and I will bring a gun to a fist fight, and old age and treachery works much better than youth and strength. Look at history to verify.
The teachers that are worth learning from don’t sell lesson or have belts or do mma. To learn a true killing martial art there are few teachers and they are mainly military only. Chinese 7th level tai chi chuan semper fu krav magra 8th lvl yeah no civilians not even most milItal. To even get there takes years of dedication to get notice of possible trainers. Learn 5 techniques learn them well and stick to them most here are beyond age of learning more than that effectively.
Am I saying not to learn unarmed technique but you will never be as good as a younger fitter person. So I carry a second gun, a maintain said weapons daily and before you could close with a knife or bladed weapon you would wonder wtf happened and why you wanted to try on the old guy bit too late now as you bleed out.
As for weapon failing don’t buy crap and do maintance, if you have to knife fight most likely you have a group coming so you are dead any ways. Killing is tough doing it hands on is more mental strength than most have yo watch as the life slips away and the body relaxes as the final gasp escapes and that face will forever haunt you.
As for not your rant on chemistry better to learn that than hand to hand, if you can make those chemicals you will be a protected resource, even if your side loses you have uses like a doctor and are not as disposable.