-What happens if the hardware wallet is defective or compromised? Is there an alternate route.
If the HW is broken, and you have a backup (seed words), you always have the choice to make a recovery in a new HW, or in any desktop/mobile wallet that accepts your seed (although this is not recommended for security reasons). In the event that your HW is compromised in such a way that someone managed to hack it, then it's game over because the attacker will send all the coins to their addresses and you will be left without everything.
It is unlikely that someone will decide to guess the PIN and be lucky, at least as far as the Ledger HW is concerned, which will be reset to factory settings after three incorrect PINs, although the Trezor has as many as 16 attempts before the device is reset, so a thief would have a much better chance to guess a very simple combination.