There is nothing which is 100% safe. But you should add something more in you points which can make you more secure.
1. Cord connection: data can still be transmitted when connecting the hardware wallet to your PC.
When you connect the hardware wallet to your computer data can still send. That why it is important to make sure your computer is secure and doesn't have any viruses or malware.
2. SD Card: some comes with Sd card option for updating the hardware wallet, but I am not sure that using Sd card can always be safe either, I remember those days where I use to buy lots of Sd card because they have issues easily and also they get viruses easily. Old Symbian and Android users here?
Using an SD card to update your hardware wallet can be risky. It is important to be careful and only use a new SD card that you only use for updating your hardware wallet. Do not use it for anything else to reduce this will make you more secure.
3. QR Codes: honesty, QR codes are not readable by the eye, they comes with blocks like figures, there is no way to know what's written in that QR code anyway, there is no way to read it and know what kind of data is inside it.
QR codes can be hard to read and understand. It's important to aware when scanning QR codes especially one you find online. Only scan QR codes from those sources which you trust like when you are making a payment to another crypto wallet or selling your BTC on a exchange.
4. You still have to rely on the company for future safetiness of the hardware wallet in terms of software updates, if someone hackers find a way to alter the upcoming update file you know what could happen.
Depending on the company for software updates mean you are rely on them. It is important to choose a hardware wallet provider that is trusted and regularly updates their software for security.