So Hanks(M. Douglas) wife is still alive?

Maybe?

If she is brought back, then to her it'll feel like no time has passed, because time is irrelevant in quantum space. Sure it'll suck that she's young and everyone she knew and loved is suddenly old or dead, but at least it won't feel like she was alone in an empty world for decades on end.

That does seem to be the implication. They were also careful not to show her face so they can always cast her later. It might have been interesting to see Janet Van Dyne in the MCU, maybe a love-triangle with Pym and Stark etc., but I'm pretty sure we've seen just about the last of Stark (once the current round of planned films is over), so it probably won't happen. But they've left that door open.

She's just floating through the microscopic universe, eternally shrinking? What does she eat and drink? When she becomes too small for her lungs and metabolism to process oxygen and nitrogen molecules, which will become larger and larger in proportion to her, how will she breathe?