If you are planning to trade your coins you should put it on exchanges because you cant trade using your hardwallet,but if you are going to hold your coins for a long time i suggest put it in a hardwallet because these wallets are most secured storage today,ledger or trezor wallet are the most common wallets that are being recommended by the experts.Exchanges doesnt allow the users to store big amounts of coins if they are not trading because exchanges is more prone to these hackers nowadays.

Yes if i had more money i would definitely buy some more,this is the perfect time to invest in bitcoin or in altcoins,you will be suprised when the market has recovered you will have plenty of money from these dips because most of the people are scared to buy when the times like this,but few are happy because they can buy a lot of cheap solid coins.

If the foundation will collapse what will happen ? alts will surely follow btc and thats the end of our world.

Yes i am very happy and satisfied with my BTC holdings alts are bleeding hard but they will recover soon.