Is it permissible to pay a ransom (fidyah) for not fasting the previous Ramadan due to pregnancy, and is fasting required now with the renewed pregnancy, caring for a nursing infant, difficult circumstances, and living abroad?

There is no need for confusion, for the matter is easy, Allah willing, and there is no sin upon you for delaying the making up of the fasts if you are excused. Making up the fasts is a debt upon you that must be fulfilled when you are able to, and feeding a poor person instead is not permissible.

The view of the majority of scholars is that if a pregnant or breastfeeding woman breaks her fast, she must make up the days. If a pregnant or breastfeeding woman breaks her fast out of fear for her child, she must make up the fasts, and the guardian of the child must feed a poor person for each day she broke her fast.

If you are unable to make up the fasts, then there is nothing upon you, and you are obligated to make up the days whenever you are able to, even if it is years later. The one who is excused in delaying the making up of fasts due to illness, travel, or the like is permitted to delay as long as their excuse persists, and they are not obligated to pay expiation for this delay.