Jinkster way too much thinking and over thinking going on regarding bike parts, etc.
Your 170mm cranks are fine and don't need replacing.
You've only made one slight mention of your bike...you mentioned hybrid in one reply...what are you riding for your everyday bike? What kind of pedals?
If you've spent a long period of time abusing your body it is going to take some time and most of all patience for your body to rebound and return to a reasonably fit form...doesn't matter what you did or did not do in the past, it is the now that matters.
Take your time, do a bit of stretching before an activity, start any activity slowly until your body warms up. Start activities slowly...don't try to do too much too fast...typical attitude, and commendable just not smart, for people recovering, trying to improve their lives, etc...
Relax and enjoy...your body will thank you for it.
Pain is a good thing...it tells you when you are pushing to hard, have exceeded your bodies current capability and/or are doing something that is causing injury or potential injury.
Typically riding a hybrid, or any upright type bike, means you are pushing in a downward motion much of the time...almost like stair climbing. If you are using standard platform type pedals you are pushing down more because that is the most stable position. The strain of the motion is more centralized thus potential for pain/injury.
If you are using toe clips/straps or clipless pedals you can and should push forward as much as downward. Also, as has been said, dropping your heels down a bit changes the load on the muscles a bit giving some a rest while others work.
Using your gears to keep the load lighter is also important...higher rpm's puts less strain than lower with more "push".
Spend time looking at your environment...enjoy the ride...your fitness will improve, you may as well enjoy the view even if it the same one on nearly every ride...we all have that "problem"...eventually you will get to know every stone, etc. on your routes.
Make sure to stretch after the ride...maybe an hour or so...gentle, light stretching is as important after the activity as before...your muscles, etc. have tightened up after the ride and need some gentle stretching. Learn some basic self massage...YouTube videos should help...and give your legs a massage after your ride while relaxing. Some people also lie on the floor and put their feet on the wall so their legs are at an upward angle to promote blood flow...try it...if it works it is good.
Keep it up...most important of all.
Cool you mention the traditional bow...I've been thinking about trying out traditional archery for a while now and am close to buying a bow, want to make one at some point. I've spent a lot of time looking at traditional long bows and recurves...probably going with a starter recurve, Samik Sage in the 25 pound range as I'm 59 years old, 5'5" at 155lbs...It looks like fun and I can shoot in my back yard, plenty of room.
Good luck and keep us informed.