I think increasing the base battery amount is the way to go. The hotel and later some other ways should restore to full. The alley was intended to be half so I would go with 3 when the max is 6. The battery booster item could be buffed to 2 as well.
Renpy is the easiest engine I have worked with. There's tons of help you can find online. The code itself is basically simplified Python. Making the images is what takes up most of my development time, especially animated scenes. I made the game's simple combat system from scratch in 2 days while the handful of enemies took about a week to make and render them all.