what reckless things has he done? it might help to know that, otherwise all we are working with is a lad out on his own walking through a park. Which, for a fit young lad doesn't feel that reckless to me.
(I live rurally so i know what it is like).
Would it help you to look up statistics for this park? to see what has happened there?
Telling him to keep his phone charged? come off it. I stopped telling mine that at about 14, which was the age i absolutely stopped picking them up from school if the bus was late. This is how they learn responsibility for themselves.
Washing and laundry? nope. I have always been happy to chuck stuff in to make up a full load, or whites or delicates or whatever, but not as a general service. Cooking? everyone staying here, temporarily or permanently, has to let us know within a reasonable timeframe (so generally before 4pm) if they are eating the evening meal with us. That is it. No confirmation, no dinner cooked for you.
Coming in late? we go to bed early ish. Coming back after that? you won't get in if you haven't told me not to bolt the door. That is a you problem. It is easier than it ever was when i was a teenager - what with family WhatsApps.
And our rule has always been: if you say no, or don't say, it is the same thing. That is a no.
ETA: cross posted with your explanation about walking in the Peak District.
Family meeting required to say why you worry as you do - not just with him so he doesn't feel picked on - and that basic courtesies are to be observed. Otherwise the "nagging" will continue.