I made many mistakes when I first got Bettas. One mistake, I believe, resulted in the death of my beautiful Plum D. Unfortunatly we must make mistakes in order to learn the right way to do things. You cared deeply for him and that is what makes you a good owner in the end.
I am sorry for your loss.
Bettas - Giovanni (HM), Burly (HMPK Giant), Potato (EEHM), Vesper (HMPK).