Difficult! My own feeling is that "well being" is a general quality of life that people feel as the sum total of many factors; whilst "welfare" concerns the more practical issue of economic sufficiency or support.
One way to approach this little dilemma might be to consider the difference between the verbal phrases "be well" and "fare well".
When one "is well", they are healthy ... when one "fares well", things (life, work, personal relationships) go well, positively, for them.
This doesn't help you translate welfare and well-being , as I would have agreed with you, bienestar for both.
That said, I think Peter's idea of "human well-being" as general quality of life, is quite on target. Perhaps as all the ways we might conceive of a person as healthy: in good physical, emotional health, with healthy, not hurtful relationships, practicing positive nutrition, getting physical exercise, (maybe bienestar intrinseco) ... while "human welfare" suggests, possibly, factors of a more material nature (bienestar extrinseco?)
Note also that "impinge" carries a rather negative connotation, as in to "mar" something. The Oxford uses it to convey "vulnerar" in the context of someone's rights.
En este caso específico, well-being puede ser bienestar anímico/psíquico, mientras que welfare puede ser bienestar material, si bien los diccionarios no hacen mucha diferencia entre ambos, por lo que su significado siempre va a depender del contexto.