Two comments and a question:
1. For the handlebars, you could bring things closer to symmetric by bending the bars back. They are steel after all. You can try a long pipe for leverage. It will not be easy but it might make you more comfortable while you wait for replacement bars to show up.
2. On the seat, I had to do that too but have realized over time that the riding position on these bikes is meant to be a little closer to the bars than you might be used to. I'm not suggesting changing anything but give yourself some time to get accustomed to the way the bike feels - you might find yourself moving the seat forward again.
3. How confident are you with JB Weld holding the sleeve? Do you have someone who has tried it and finds it acceptable for the sift cable? On my to-do list is to fix up one of my older cables (I DID use the more modern attachment temporarily) but was going to solder the tube in place. I LOVE JB Weld but wasn't sure about it for something like this.
Keep the reports coming.....I put larger sprockets on the back of all of the family 3-speeds and our collective knees have been thankful. Its not like the 18T was bad, but the larger sprockets just made the bikes more relaxing to ride.