Thanks for all the responses.
To answer the various points, etc:
That darkness you see around the nut is not a squeezed o-ring. It’s just darkness. I can’t get a clear close up picture, but the nut is actually flared back slightly where each flat side meets, thus creating that dark spot.
That hose that I’ve been trying to get off first is not leaking. The hose that has the leak is the one in the picture below with the red x. That is a new hose that I put on two years ago. The problem is that I have to remove the other three hoses first in order to get at the hise that is leaking.
View attachment 1291650
The wrench that I have used successfully two times before is this open ended basic crescent wrench
View attachment 1291880
When I put the hoses back on the prior two times, it was just me hand tightening it with the same crescent wrench; did not use any power or air tools, or any type of thread lock.
I do have more than enough room for leverage. It’s just that I cannot get whatever I use to grip the nut to lock it tight so as not to strip it.
Might just put super glue around the leaking fitting and call it a day……..(I’m joking).
I’ll figure something out; had just been curious if there was some tool out there that I wasn’t aware of that would make this a simple job.
Thanks again to everyone.