I would perhaps be quite suspicious if the car drove fine for fifty miles and reverted to it's former ways.. Alignment problems could contribute to some of your problem as well. Either way I would get this car up on a hoist and check out alll suspension components. Some with a pry bar if indicated.
You mught check your upper sway bar mounts, bushings etc. before the hoist work. Use a little pressure to make sure everything is solid. Also make sure no suspension point is semi mobile because of invisible rust hidden under the undercoat. Those guide rod mount points should be really solid. Your initial description would make me check the rear end area as carefully as the front. Something is probably moving too much under pressure. Use a pry bar. R.Leo is mentioning the type of thing to look for that is bad if not the actual item.