This should be obvious, but Electrum which included on Tails isn't up-to-date. Bug regarding wallet/seed creation don't happen and new address/wallet standard rarely changed, but people should know about this fact.
6. Burn the USB. If you are very paranoid, burn the computer too.
This is completely unnecessary if you use linux that only runs at RAM or you use CD-R/DVD-R as boot media. You also could remove all storage drive, leaving only your USB, CD-R or DVD-R if you're that paranoid.
Also, it's not really good action from environmental side.