You might consider putting a 3x front on that bike. With the 8 speed 11-28T on the rear, you'll have a lot more gear combos available to you. And when in the small front ring be even lower ratio than the 34/34 of your original configuration.
Though you'll have to find a new or used 3x crank and BB that will work on your bike. If you are indexed shifters, then you'll need a 3x indexed shifter too. But conceivably less than 100 bucks if you can do the work.
IMO, if I was climbing a hill at less than 70 RPM for an period of time I'd have sore knees. My normal cadence for anything is 85 to 95 RPM. I haven't had knee issues for a long time.
Last edited by Iride01; 09-10-21 at 03:37 PM.