This won't help you, but I found the old fuel gauge for my 1978 E30-2 in my bilge last week while troubleshooting a fuel tank leak. I was not aware that my boat ever had a gauge. I also found several sections of old brittle thin hose similar to what you describe. My leak occurs only when I fill the tank all the way, so I filled it and found that fuel was shooting out of a piece of that small hose that is still attached to something on the top of my tank, presumably a fuel level sender unit mounting plate. I think that you can possibly anticipate the development of such a leak in the future when your hose gets brittle and breaks.
I believe that sending units are normally have electric sensors, not a pressure sensor like I apparently have fitted to my tank. This does not amuse me - I can only hope that I can somehow access the hose fitting on the tank without unreasonable effort - such as removing the engine and tank. I will either plug the hole or install a different sending unit (only if I am lucky enough to have the standard sending unit bolt pattern on top of the tank and can do so without removing the tank, which has only about 2 or 3 inches of clearance below the cockpit sole). I could cut a hole in the cockpit sole over the sending unit location and put an access plate there - but since I have my wheel mounted on the sole, I'm hesitant to weaken the sole in this area.
If I find out anything useful about the sending unit or its mounting, I'll let you know. The broken gauge seems to have been made by Marcra? Mfg in Costa Mesa, which doesn't exist anymore as far as I can tell.