Importing paper wallet into Electrum

I’m attempting to understand the workflow of sending bitcoin to a paper wallet and retrieving it. I’m using small amounts until I get the hang of things.

I’ve created and sent bitcoin successfully to my paper wallet. Here is my paper wallet public key:

https://blockchain.info/address/1581DNnh8tmHFd2YS7kAorppibGMehScnv

With two transactions having gone through, and a balance of 0.0004 BTC.

I’m now trying to import the private key into Electrum (version 2.9.0).

I’ve taken the wallet private key and decrypted it using bitaddress.org (I used a BIP38 passphrase) and got the Private Key WIF (the 51 character one that begins with 5). I then go to my primary wallet in Electrum and go to Wallet > Private Keys > Sweep as there’s no option for import (it looks like as of v2 Electrum no longer supports importing private keys).

I enter my Private Key WIF and I get the following message:

“No inputs found. (Note that inputs need to be confirmed)”

My first question is, what does this mean? My assumption is that this means that there is no bitcoin associated with this address. I thought this could be because the wallet didn’t have enough bitcoin attached to it – that somehow there wasn’t enough to pay the mining fee. (Thus the two transactions).

My second attempt was to create a Standard wallet from scratch, using the private key. I did this and the imported public address matches the one displayed on bitaddress.org post-decryption. However, the balance in this address reads 0.

I really want to make sure I understand how this process works from start to finish. To summarize my questions:

1. What does “No inputs found. (Note that inputs need to be confirmed)” mean?
2. What is the recommended procedure for retrieving coins from paper wallets?
   Should you sweep them into an existing wallet, or create a wallet from scratch and then send them to a different wallet immediately?
3. Given that the wallet here has transactions associated with it, why would my imported wallet – whose address matches this (although the address in Electrum is the decrypted address, and the one on blockchain is the encrypted address) – show zero bitcoin associated with it?

Thanks for helping this bitcoin noob!