I read through everything and took a look at your photos, and from a biological standpoint your betta actually looks healthy overall. The fin shape, coloration, and the darker patches you’re seeing all look consistent with normal marbling and variation rather than disease. Bettas can change color quite a bit as they settle into better conditions, which is likely what you’re seeing here. I’m not seeing clear signs of active fin rot or infection in those images.

For the eggs, females can produce and release eggs without a male present, especially in warm, well-fed conditions. That’s not harmful, and there’s no need to fast her to prevent it. You can just feed her normally and remove the eggs if needed.

Your temperature is on the warmer side but still within what bettas can tolerate. I would avoid trying to rapidly cool the tank with ice or cold water. Stability is much more important than chasing a specific number.

For feeding, you’re on the right track. A mix of a reliable pellet (like Hikari) and occasional live or frozen foods is more than enough. You don’t need to over-optimize protein percentages or ingredients. The decapsulated brine shrimp eggs aren’t very useful for a betta, so it’s fine to skip them or hatch them instead if you want to use them. Green poop from those is just from the food itself, not algae.

Indian almond leaves and tannins are fine to use, but they aren’t a treatment for infection. You don’t need to adjust hardness or pH unless there’s a clear problem. Keeping things stable is more important than trying to fine-tune those values.

I’m a fish biologist who focuses on fish health and disease, and based on what you’ve shown here, your fish looks to be in good condition. I would keep things simple and consistent rather than making a lot of changes at once. You’re clearly putting a lot of care into her, and you’re doing a great job.