Is the questioner considered undutiful to his parents after they expelled him from the home due to his financial situation, and who is in the wrong in this situation?

You must try to mend your relationship with your family and seek Allah's help in doing so. You can also seek the help of relatives and friends to mediate. It is not permissible for you to sever ties with your family and kin, especially your parents, because cutting ties of kinship is a major sin. If you maintain ties with them and forgive them, then Allah will be with you and will support you, as stated in the noble Hadith that whoever maintains ties with his relatives who cut him off, it is as if he is feeding them hot ashes, and he will continuously have a supporter from Allah against them. Therefore, fulfill your duty towards your family even if they do not fulfill their duty towards you, for Allah will grant you victory.