Workers' compensation laws provide money and medical benefits to an employee who has an injury as a result of an accident, injury or occupational disease on-the-job. It is intended to benefit the employee and employer alike. The employee receives money (usually on a weekly or biweekly basis) and medical benefits in exchange for forfeiting the common law right to sue the employer. The employer benefits by receiving immunity from court actions against them by the employee in exchange for accepting liability that is limited and determined. The question of negligence or fault is usually not at issue. I would encourage you to consult with a licensed attorney in your state (if you haven't already done so) in order to specific information as to your rights in your state.
Generally, you cannot sue your employer for a work injury. Workers' compensation is a trade-off, where you can collect benefits regardless of fault and your employer does not have to defend a lawsuit. Sometimes, a lawsuit may exist separately, such as against a third party or if you were intentionally injured. As far as settlement, insurance companies almost always give low offers. Having an attorney usually helps. If you need a referral, let me know. 1-800-807-9530.
You did not state if you have an attorney. If not, I would suggest you consult with a local attorney experienced in handling worker's comp cases ASAP.
In most situations worker’s comp is your only remedy, which means that you cannot sue your employer for pain and suffering because pain and suffering is not an available remedy in the worker’s comp. system. Given your description of what has transpired so far you need legal advise to pursue all available remedies you are entitled to, including permanent and total disability if your doctors agree.