Bipolar Planter Facistiis

I have been diagnosed by 4 different docs as having bipolar planter fasciitis. I am a refrigeration technician and am up and down ladders w/ very small rungs all day long. I have not been able to work on over 2 months. I am significantly overweight. The following is a list of what has been done for my feet with the results.
1. Night splints---unknown if it helps or not much difference between wearing them and not.

2. Taping using the low dye method---50% reduction in pain

3. Physical Therapy
Ultrasound---no effect
Misc. stretching and exercises---minimal effect
Aligned my back and hips---good results, not sure why

4. Cortisone shots (2)---minimal effect

5. Custom Orthotics ($480.00)---pain is worse, no warranty (GRRRRRRRRRR)

6. Medrol Pack---did not help my feet and made me very unlikable for about 4 days

7. X-rays---everything is normal

8. Nerve Conduction study---all normal

9. Daily icing and hot packs on feet. (I alternate back and forth several hours each day)

10. Birkenstock foot beds---these have helped more than anything.

I can walk on a concrete surface for about 40 min before the pain becomes unbearable

Using trekking poles I can walk a couple of miles before the pain forces me to quit

My doctor says that there is nothing else that can be done to get me back to my job.

He has told me that I am not a good candidate for surgery due to weight and the intense level of activity related to my work.

I have a family and am at my wits ends as to where to go from here...

Any help would be appreciated