1. They are expensive, that is why people that store low amount of cryptocurrencies prefer to use online wallet. But storing coins worth more than 1000, hardware wallet is recommended.
2. They are not convenient to use like online wallets that you can easily access and trade.
3. A malware from hackers can erase the address code a donor is sending to while
sending high amount of bitcoin. The address will be replaced by the hacker's bitcoin address. This could happen to altcoin of high amount too depending on the malware.
4. The random number generator can be insecure and create a private key that can be known to hacker.
2. That depends on HW wallet and wallet (which used to connect with HW wallet) you use. Ledger HW wallet and Ledger Live is quite convenient, even though the feature is limited for power user.
You are right, the ledger nano x is portable and can can be use with a mobile phone through bluetooth. Although, if you use the ledger live app, you are limited to 23 cryptocurrencies. But, I think that is good enough. For more, you have to access it through desktop wallet like electrum. But, for me, 23 cryptocurrencies is good enough to use ledger live. You are right.
I just want to add that you can create your own de facto hardware wallet with a USB Flash Drive with these simple steps
One of the main advantages of hardware wallets, in addition to keeping your keys permanently offline, is that if they fall in to an attacker's hands your coins are still safe (or at least, safe for long enough for you to recover your backs ups and send them to a new wallet). Your set up misses out this important protection, unless you are also encrypting the USB drive.
Yes, you are very right. If the hardware wallet is stolen, it will be difficult or not possible to get access to the private key and seed phrase by the pilferer . So, only what the owner will lose is the wallet. He can order for another new wallet from a trusted and reputed seller but ordering from the the company itself it advisable. So, after, he can retrieve back the cryptocurrencies.