As you can tell from my last post, I’m simply a parent who researches not an AO, but my recommendation would be to carefully consider if and how you mention the game development studio. You already have plenty of other activities where you demonstrate leadership and creativity and listing a development studio that is “not an official studio” and that hasn’t released any games could be perceived as padding. I’m not saying it is padding, but you want to avoid creating that impression because once you’ve created that question it could color a reader’s perception of your entire app. Quality over quantity.
Also, I should have clarified in my last post that my observations were about grades and scores in general, not necessarily your exact scores. For colleges that require or strongly recommend (which means require for most students) subject tests, you are absolutely going to need to raise your subject test scores to have a decent chance of admissions. Especially for colleges like MIT. Your ECs will not compensate for sub-700 subject test scores and we’re hearing rumors that even bare 700s aren’t even enough at the top selectives any more. So study hard and get those subject test scores up. Good luck.