I noticed numerous sidewall cracks
As rubber deteriorates and ages, it becomes harder and cracks, hence the appearance of cracks in the side wall.
I wouldn't try riding with tires in this condition as the grip will be seriously compromised and might lead to an accident.
If your riding is mostly on road, get a set of Avon Road riders as Allen suggests, these tires have a modern rubber compound with excellent grip, I use them on my Commando and A65 and they are great.
Not sure how the K70s compare to the Road Riders, maybe others can chime in.