1. Before you should consider your potential payout here, you should at least be aware of your legal rights. YOu seem to be unaware that under the Equal status act, an employer is liable for all acts of bullying or harassment which occurs at work. It makes no difference that the employer was not involved and it merely was by one employee on another, the employer is liable as well as the employee. So you should be getting full pay if you are off sick as a result of being bullied at work. Additionally, you are entitled to your job and should not be forced to leave. Additionally, should you have to leave your job, then it is an unfair dismissal and you are entitled to two years pay (80k) plus any other losses you have suffered, such as medical expenses and any losses which flow from losing your job.
2. None of the details of how the company are handling your case changes my opinion. However, you should have notified your employer about the bullying earlier when you went off sick.Ultimately, you need to be willing to litigate should the settlement offer not be sufficient.