I'm sorry to hear you are not getting along with it in the fine details because from the top level it looks like a pretty good bike. It's a pity that it's a pull-pull shifter and you can't just use any old thumbie.

It's maybe possible to get lower gearing out of your belt drive with a pulley swap. You'd probably want a shop to help with this to make sure all the parts match interfaces. It looks like the front pulley is as small as it can go so you'd need a bigger rear pulley which would also need a longer belt.