Front end wobble has progressively gotten worse

You did a perfect job of describing a broken belt in a tire. When you feel the wobble in the seat but not in the steering wheel, expect to find the broken belt in a rear tire. A pull to one side is more likely to be caused by a defective front tire, but a rear one can do that too.

Once the tire is raised off the ground, the first type of broken belt is really easy to spot. Spin it by hand and watch for a hump, or "tumor" in the tread, or the tread pattern squirms sideways as it goes around. Be careful when running your hands over the tread as this is often accompanied by steel wires sticking out. They really hurt when they poke you.

The second type of failure is harder to identify and may need the help of the people at a tire and alignment shop. The tread surface can look perfectly smooth and straight, but if you look at the deepest part of the grooves, you'll see them rise up in one spot as the tire is rotated. The tread is coming apart relatively slowly, then the high spot has plenty of time to wear flat. The break is still there, but there's no hump in the tread to make it obvious.

Here's links to some related articles you may find helpful:

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

https://www.2carpros.com/articles/how-car-tires-work

https://www.2carpros.com/articles/wheel-removal-and-re-installation

https://www.2carpros.com/articles/steering-wheel-shakes-when-accelerating-or-braking

An additional clue to finding an elusive broken belt is to look for a bad tire wear pattern in just one section of the tread. If the wear is caused by an alignment problem, the wear pattern will extend all the way around the tire.

You did a perfect job of describing a broken belt in a tire. When you feel the wobble in the seat but not in the steering wheel, expect to find the broken belt in a rear tire. A pull to one side is more likely to be caused by a defective front tire, but a rear one can do that too.

Once the tire is raised off the ground, the first type of broken belt is real easy to spot. Spin it by hand and watch for a hump, or "tumor" in the tread, or the tread pattern squirms sideways as it goes around. Be careful when running your hands over the tread as this is often accompanied by steel wires sticking out. They really hurt when they poke you.

The second type of failure is harder to identify and may need the help of the people at a tire and alignment shop. The tread surface can look perfectly smooth and straight, but if you look at the deepest part of the grooves, you'll see them rise up in one spot as the tire is rotated. The tread is coming apart relatively slowly, then the high spot has plenty of time to wear flat. The break is still there, but there's no hump in the tread to make it obvious.

Here's links to some related articles you may find helpful:

https://www.2carpros.com/articles/jack-up-and-lift-your-car-safely

https://www.2carpros.com/articles/how-car-tires-work

https://www.2carpros.com/articles/wheel-removal-and-re-installation

https://www.2carpros.com/articles/steering-wheel-shakes-when-accelerating-or-braking

An additional clue to finding an elusive broken belt is to look for a bad tire wear pattern in just one section of the tread. If the wear is caused by an alignment problem, the wear pattern will extend all the way around the tire.