At slower speeds my car rocks like a boat at.

This sounds typical of a broken belt in a tire. That is common enough that any competent mechanic should be able to find it. Have it inspected at a tire and alignment shop. Also, both front tires are leaning to the left causing the accelerated wear on those edges. That's called "camber" on the alignment computers. Tires want to pull in the direction they're leaning so the car should be pulling hard to the left when you let go of the steering wheel. If it does not, they may have set them that way during the alignment to offset a pull to the right caused by the defective tire.

If the bulge in the tread of one tire is not obvious, switch the two right-side tires front-to-back to see if the symptoms change. If they don't, switch the two left-side tires.

The location of a bad tire can be misleading. When it's as bad as you described it is usually pretty easy to see when you spin it by hand. Be careful though when you grab it because sometimes the ends of the steel wires stick out and they really hurt when they poke you.

Spin each tire and watch the tread for a bulge, a tumor, or a wave from side to side. Those bulges don't have to be very big or obvious. Next, look at the tread depth in every groove all the way around, then look at those grooves as you spin the tire. Very often the belt will break, a small tumor or raised area will form, but it will wear off from driving. The part of the tread that contacts the road will be true and flat but there may be a spot on one of the inner grooves that has a noticeable hump in one spot. While that will make the tread surface appear okay the sidewalls will flex differently in that spot and let that corner of the car drop down a little with each revolution.

You'll see numerous little raised spots in those grooves. Don't confuse those as a broken belt. Those will form the wear bars that show up when the tread is worn out. Those are about 1/4" wide. If the belt is broken the raised area will be a couple of inches long.

I'm not familiar with your car model. There are a few out there, mostly Ford products that have very poorly designed suspension systems and tires wear out three times faster than normal.

The first thing is to keep an eye on the alignment. There's three things to look for. When you let go of the steering wheel on the highway the car should go reasonably straight. If it pulls to one side, "camber" is off on one or both front wheels. That means a wheel is leaning in or out on top too much. It will cause accelerated wear on the edge of the tire. If one wheel is out-of-adjustment that won't affect the other one. A tire can cause a pull too and not really be defective. Often you can rotate it to the back and not have any more problems.

"Toe" is the direction the wheels are steering when the steering wheel is straight. If the front of the tires are too close together or too far apart it will create a "featheredge" pattern on both tires. Both wheels could be out-of-adjustment or just one could be. Usually that will also cause the steering wheel to be off-center when you're driving straight ahead.

Those three things to watch are steering wheel position, pulling to one side, and tire wear. Check the air pressure regularly. There will likely be a sticker by the driver's door that lists the recommended pressures. That is the minimum safe pressure that will provide a comfortable ride. I always made my customers' pressures higher for better tire wear.

Rapid starts and hard stops will cause more tire wear than normal highway driving.