Hello and welcome to JustAnswer.
I'm sorry to hear about your situation and hope I can help.
1. No, you cannot be terminated while you are on FMLA protected leave for a disability.
2. No, the determination of whether you are eligible for Long Term Disability is made by the insurance carrier, not your employer.
3. Unfortunately, unless the HR Manager's harassment of you was based on a protected characteristic, it isn't illegal, so you can still file a complaint with HR, but you would be unlikely to recover for lost wages and punitive damages against the HR Manager or your employer for the claim.
4. Yes, I would recommend that you file for workers' compensation if you are unable to work due to your disability, and are not planning on being able to return to work in the near future.
I would suggest that you hire an attorney to assist in your workers' compensation claim.
You can find an attorney to represent you online here:http://www.lawyers.com/Workers-Compensation/California/browse-law-firms-by-city.html
Since you don't have to compensate a workers' compensation attorney unless you are successful in obtaining a settlement or verdict in your favor, you have nothing to lose by hiring a workers' compensation attorney to assist you in filing your claim.
5. I cannot think of any additional suggestions for filing for Long Term Disability.
6. As I mentioned before, I suggest that you do hire an attorney to assist you in filing your workers' compensation claim.