It does look good. I've used sweat unions that are foreign and threaded ones that will hold up if installed with tape and thread sealant , with no prob.
Why ya have to replace valve? Can it be rebuilt?
I will disassemble the leaking one, and if possible toss new parts in it. Question though, if it's just the seal around the lever leaking, can that be replaced without opening the valve body? If not I'll have to cut the copper so I can un-screw the valve body.