This is a really cool project - it's incredibly difficult to achieve a convincing physics simulation, let alone astrophysics, so what you've done so far is incredible for a free indie title! I enjoyed creating my own little system and seeing what made it hurtle into the void.
I think you're on the right track in terms of development around thinking about the parameters for the simulation and how the physics and the properties of planets and systems can do their own thing. Simulations are fun because they have an emergent quality and players like me enjoy tinkering around with things and seeing how things react. It can be tricky trying to think about how all these properties integrate meaningfully and provide feedback to the player, whilst not getting too lost in the impossible depth of physics theory!
Congrats and great work on building this game to the state that it is. I enjoyed playing it a bunch.