I don't think a cat crying outside for hours and getting into fights with chunks of ear missing sounds 'happy'. Especially since it is going to be cold there soon.
If it is a ferral cat, you can adopt it, love it, and it will run away. But this cat sounds like it wants to hang around. (I adopted a ferral cat, he was so sweet, but disappeared one day!)
I would bring it in, get it fixed, and definitely have it tested for parasites, feline leukemia/aids. Then have those shots given, since those disease are very contagious for cats. Losing a lot of weight could mean it is hungry, or could be a sign of sickness and/or intestinal parasites. The humane society in your area may have a catch and release program for strays in which these health care costs are lower. Call and ask.
Be sure to have a scratching post for the cat inside, or you can even put rubber claw cover on the nails, since declawing is a very in depth and painful procedure, especially for an animal that may run away and try and survive outside again.
I've worked in vets and animal shelters and this is the absolute best thing you can do for this cat!