Maybe your biological parents sent you to foster care for their reasons! In the 1980 s, the economy was not good and life was difficult to guarantee. Forgive them! As you said, parents are bigger than the sky. Although your biological parents didn't give you any care, they gave you the most precious life-nothing can replace it.

Today's biological mother is ill in bed. Anyway, you are related by blood. Out of respect for the elderly, support some financially! However, emotionally, you should call "Mom", because the old man is so eager to have the support of his children at this moment-in fact, you are already supporting your mother in your heart, but you still have some hatred for her, hating why she didn't leave you around at that time!

More tolerance! I believe your mother will get your tolerance and her body will recover faster.

Hope:

Happiness!