Is it possible to donate the amount allocated for Hajj on behalf of one's father instead of performing Hajj, due to the inability to perform the obligation, shortage of money, and increasing Hajj costs?

If you can add to the remaining money what enables you to perform Hajj on behalf of your father—provided you have already performed Hajj for yourself—that is better than giving charity on his behalf. Hajj, performed in the prescribed manner, is better than voluntary charity. However, if you fear that the money will run out, then give it as charity on behalf of your father.