OH SH111T!
I just did something STUPID, and I don't know if I lost all my BTC. My heart is beating so fast now, and my hands are shaking.
[...]
I'm praying and hoping it's nothing, and I've just deleted an unbroadcast transaction, and that I haven't lost my BTC irretrievably.
You should really first learn how bitcoin actually works.
The coins are
not stored inside of your wallet.
The coins are assigned to your public key on the blockchain. Your wallet holds the private keys.
As long as you have access to your private keys (by having a backup of your mnemonic code), you won't lose access to your coins.
When you somehow fail to send a transaction, the coins can not be lost. They either are assigned to your public key or if you send a transaction, they will be assigned to the recipients public key. There is no in-between. There is no "limbo".