25,000 bitcoins can be sold for about 5 1/2 million dollars. I would sell 24,000 of them and put the proceeds into conservative dollar denominated investments. This money I would use for real estate, retirement and my children's businesses.
This is off topic. What you would do with the amount of coins is not relevant to his questions.
dont store all your BTC all in the same way, with the same website etc. when there is one mistake, you lose all.split your funds. you can use:
1. hardware wallets
https://bitcointalk.org/index.php?topic=899253.02. paper wallets
3. Xapo.com
buy a good antivirus and maleware programm.
I agree. Especially using a online paper wallet generator (which people often do) and print it out via a printer that is connected to the network (as a second example). So many things could go wrong here in case of security. It's best to use at least 1 different method per wallet (since they're only 4). Xapo seems good these days as well. Technically if he were to encrypt his wallet.dat properly he could leave it online in any server and not worry about it. Encryption is very important. Even if someone finds your wallet.dat, USB stick or whatever device is used, without the password they can't do anything with it.
However, this really depends on what OP wants to do/has already done.