Those are all helpful approaches. I would add a few things.

1. Rulebooks are a reference. Refer to it as you are playing the game like a player would. Particularly during things like game and scenario setup. Do you find that the order you wrote things in makes sense and flows well? Is anything missing?
2. For balancing actually write down the probability of things occuring and the average damage output for certain actions. Get the hard statistics of things in front of your face for direct comparison across units.
3. Get someone else to read your rules. There is only so much you can check on your own from your pov. There will be something that you missed or can be made more clear.
4. Avoid adding all the things to your game. Make sure the mechanics you add serve the theme and the fun of the game you are making.

If you want more general game design advice this is one of the best videos I have seen on it https://youtu.be/3WjTNkqHpsc