Regarding "could cause damage to my knees/body if I continue to do this without losing weight or increasing power".
For a given grade and a given gear (34f 30r) increasing power will not reduce the stress on your knee. To go faster (higher cadence - more power) in gear X and hill Y you need to push harder.
The only thing that is going to reduce pedal force is less weight or a lower gear. Same answer as Eric (+1+).
34f 30r is a fairly low gear. You Your muscles may be out of shape but your knee is not out of shape. If you don't have knee problems you should be OK. Unless you are carrying a lot of extra weight.
I would go ahead and continue to train with 34f 30r and if you get knee pain then you are going to need to go with a smaller gear or a smaller hill.