Unless I'm missing something here, you removed the wrong nut when taking the hose out. The first nut, as your picture indicates, has no compression fitting at the end - most likely there was a copper or aluminum crush washer between it and the pump housing, or possibly an o-ring in a groove on the housing itself. The second nut is the one that should have been loosened, while holding the first nut with a backup wrench.

You need to find any washer or o-ring that was used to seal that fitting before you re-assemble. If the fitting was bottomed-out against the housing, there's a seal there somewhere. Regardless of which type of seal it is, it should be replaced when you reinstall the hose - cheap insurance against leaks. If the seal is an o-ring, the replacement (in my opinion) is mandatory.

Of course, if you tried that and were unable to get the second nut to budge, your method of removal would have been the only logical choice, and would have resulted in the spaghetti hose you would up with.

It's not repairable, as you surmised. In general, hoses like this that carry fluid, especially oils, are a royal pain in the butt to even attempt to braze or weld. You can never get the metal clean enough that oil doesn't ooze from somewhere and spoil the welding/brazing effort.

Good luck.