Why don't you buy aftermarket gauge with sensor and put it in the top hose?
Or capillary gauge if you know what the thread in the housing is.
Saves buying endless sensors which are not compatible.
Have you tried earth on the gauge which someone previously suggested?
By the way even if you do...
No swarf in ours at all, ran perfect with no smoke for 9 years until it didn't.
You can buy clear pipe in B&Q to use on a temp basis or clear fuel pipe on Ebay.
It's possible that your pump needs a rebuild, your symptoms are pretty much the same as my son's 200tdi. We exhausted every other option in the vain hope it wasn't the most expensive part in the system.
Having just had a new clutch fitted on a 200tdi it made no noticeable difference to the lightness of the pedal.
Remote servo shouldn't cost a great deal in parts, have a chat with your local specialist. It will be the best option for your medical needs.
Fit a remote servo for the clutch, it will be as light as a feather then.
I have one on the Td5 and it really is no different than my modern car, it was fitted by the previous owner.
Can't see why you can't fit one on a tdi.