I actually never heard of this hardware wallet yet and it seems secure what you did however are you sure it’s considered air gapped?

You said you saved the signed transaction onto an SD card and you later put that SD card inside a online computer to broadcast. So that’s not air gapped.

Air gapped would be if you used QR codes back and forth. Honestly it really shouldn’t matter because it would be very difficult to infect the SD card and hack the Hardware wallet but it’s a precaution you can take.