CLOSURE:
1. I ended up giving my male quail back to the seller that I bought him from. Luckily this seller doesn't kill his quails for meat

, only keeps their eggs. I feel bad that my quail had to witness all of this, but he's in a more secure environment now(with a harem of female quails of course).
2. I *somewhat* figured out what happened to my female quail that died. On that same day, I told my family members about what happened, but guess what, they already knew about it. Turns out that long before I woke up, they found half of my quail's body outside the cage and the other half inside the cage, but stuck in the wire. So we're guessing that she was sleeping next to the cage, when some predator tried pulling her out. However, that predator was unsuccessful and only able to drag half of her body outside.
3. ALSO, my other family member told me that he had seen a black cat watching them for a while, but never bothered to tell me because he thought the cage would protect them.
So I'm guessing that it was the black cat that killed her...
I see it walking around the neighborhood every now and then. I feel so sad and angry, but can't do anything about it

Anyway, I learned my lesson. I don't think I can raise quails again because I feel so guilty. Actually, I can't even if I wanted to. The family member that first discovered the body in that shape is *extremely* traumatized, even till now.
***Advice to newcomers, make sure to keep your cage SECURE as possible!!!