I enjoy training by HR and do all my easy and medium aerobic days based on that. I don't think HR is best for anything faster than tempo work. And even with tempos I'm going off of feel more than HR.
I also don't think training in HR zones based on max HR is a must. I know some people love that, but as has been pointed out, max HR is super tough to find, and it can move around depending on what shape you're in. Sill, wearing the watch in some hard races and interval sessions just to see what you hit is a good idea.
As to your 160s on easy runs, that is most likely too hard. At your age I'm guessing you will be around 140s but more likely low 150s for easy runs. This is where you should play around with the watch. Go do some runs where you never leave the 130s, do some runs where you never leave the 140s, same with the 150s. Pay close attention to how everything feels.
I personally do all my easy runs in the 130s and my slightly quicker but still not hard runs in the low 140s. But I'm twice as old as you. My goal with this is to gauge effort and slowly get faster in those specific ranges. I am of course also working to get faster in workouts and races.
I have not been playing around with this for very long, but it is fun. In the winter the low 140s had me around 9 minute miles. Now the 130s has me in the high 7 minutes. Recovery is sooooo much better for me than it used to be.
For now, I wouldn't worry about how slow you go on your easy days. I don't think you need to drop to 10 minute miles, but see how the low 150s feels. If you haven't been spending any time at these lower heartrates, then it will take time to get faster in them. But when you do, you'll find you get faster at all the higher heartrates, too.