I tried so hard to get my first cat to walk on a leash. He hated it. He longs to go outside, so sometimes I'll put him on and try again. He gets so frustrated though! Hope you have better luck than I did!
In the first picture, it looks like your cat's wearing two neck collars (one of which belongs to the harness)... is that possible, because it seems like a little overkill for such a small cat to deal with, though I understand you're wanting to have one with ID on it (if that's the case). Would it be possible now that you have the new one, to maybe either microchip the cat instead of the orig. collar, or else use a lighter, narrower one for the ID?