The other 2 replies have most questions covered already.
Concerning anti-virus, a small explanation here.
Anti-virus is not necessary to keep your coins safe as in your coins being hacked, coins cannot be hacked from your wallet.
But if you have a virus on your PC that keylogs your mnemonic phrase or wallet password, then your coins could be stolen.
Same goes for a virus that captures your screen and snapshots the mnemonic phrase while you create your wallet.
That is why anti-virus is important, to prevent the "access data" (mnemonic phrase, password, private key) to your coins from getting stolen.
Your coins themselves cannot be stolen by a virus, only this "access data".
But as said with the data gone then your coins are at risk.
Hope to have this cleared up a bit for you