How safe is this using MEW offline?

I have a offline computer as cold storage with encrypted files holding my crypto. I use MEW offline

I go on my offline computer and use a password to decrypt, I open up my wallet through MEW offline and generate a transaction. I insert a USB stick and and copy and paste the transaction onto the USB, then insert it into my online computer and open up MEW and paste it in.

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My concern is that somehow I would download a bad version of mew or somehow a virus would get onto my USB stick and change the MEW files in my offline computer to either

1. store the encrypted file with password onto my USB stick
2. Change the UI to change the address/coins that I am trying to transfer to. For example, what if I wanted to send 1 ETH from A to B and when I copy that transaction generated into my online computer, it really sends all my ETH from A to C.

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Idk, is this really a valid way of keeping my funds secure? My password is not decryptable so I am not worried about people getting their hands on the files. I just don't really understand the point of using a ledger because isn't this the exact same thing?