Dying Sycamore Tree?

Hello botanists!

We moved to our home two years ago, and one of the things I love most about our property is the plethora of massive trees! I have always been especially drawn to this massive sycamore, and could only imagine how much it has seen in its long lifespan. While I noted the large split in the tree when we moved in, it seemed relatively healthy at first.

I’m noticing some concerning things this spring. Nearly all of the leaves in the lower branches are dying off, and there are more branches falling than usual. I additionally am seeing a TON of ants, and many areas that appear rotted.

I know virtually nothing about trees, however from what I’ve googled, I noticed some other signs of poor health, such as rough bark at the base of the trunk instead of the signature splotchy pealing bark and a mass of smaller, thinner branches towards the bottom.

What steps can I take to help my tree? Is there anything I can treat/provide to help it recover? And what would a good age estimate be? I would love to save it if possible!