To follow up on this bent breather tube...today I went ahead and fixed this. At least, I think I fixed it.
So what I did was, bent the broken tube back into place. Then I tested it for pinching - I inserted a plastic zip tie into it, just to see if it goes through. It does, but it jams in the pinch unless I twist it. That was expected, as the pinch is just perpendicular to the angle the zip ties goes in.
Anyway, I used JB Weld which I put around the whole tube, as the lower part of the breather tube wasn't completely stuck in the diff cover, but it was possible to rotate the tube if tried.
I know there was an option of changing the differential cover altogether, but this wouldn't work for me, as the high capacity covers interfere with the additional diff brace that I've got installed.
I don't doubt that this fix will hold, I'm just wondering whether it will seal it well, or am I looking at the oily diff cover every few weeks....