I'm sorry you have to go through all this. It's not right.

As much as losing this job would cause your illness to worsen, it sounds like keeping it is also worsening your condition. Have you tried to look for another job at all? I would definitely consult an attorney at this point. And document EVERYTHING. Keep a paper trail of every communication with your superiors regarding your disabilities. Only notify them of appointments/accommodations/etc by email. Send things with receipt notifications enabled so you can prove they got them.

Oh, and not to muddy the water, but if your ADD is affecting your job, you can list that as a covered disability and request accommodations for that as well. Do remember though, that legally they do not have to honor an accommodation if it would pose a real hardship to the company in any way. But they do have to try.

But the ridicule, harassment, and denying you your treatment times is definitely illegal. Your treatment appointments are covered under the Family Medical Leave Act, provided your company has at least 50 employees and you've been there at least a year, which you said you have. They have to allow you time for treatment appointments as Intermittent Medical Leave. The time used comes out of your annual FMLA allowance of 12 weeks, and can be in as little as 15-minute increments. If you call in sick due to your illness, that is also covered under FMLA, as is of course any hospitalization. But you need to let your employer know it is an "FMLA day" for it to be covered.

But definitely get that attorney.