One is bigger then the other
If you do not spend your money or valuable items wisely, you will not benefit from it but instead sink in your own despair.
Answer:
When my brother finally got back from serving overseas, my family was happy and proud.
Explanation:
It should be
When my brother finally got back from serving overseas (Pause) my family was happy and proud.
So yes, a comma is needed
Past participle is the answer