In my opinion KNN is actually easier to get good results with but much more difficult to get spectacular results with. My current KNN gun in Nene is pretty much bare bones (being from Mint). But I had started to hit a tweaking wall with it despite only having 'good' performance.
I strongly doubt that you hit a tweaking wall with your attributes. Try:
making sure all of them are calculated correctly
working on your segmentation for wall proximity
perhaps tweaking how your bandwidth and size of k