We can't know the answer to your first two questions yet, because we can't see the code and we don't know if there is replay protection. Assuming there is replay protection (address format change), you should be able to send your legacy coins to a new, safe wallet first. Then you can safely extract the old private key (to the address that held coins before the fork) into a Bitcoin Gold wallet.

Nobody knows how markets will be affected. I wouldn't listen to any speculation/investment advice that you get in Bitcoin Discussion.

Some exchanges gave their client bitcoin cash last split. I know bittrex did it. Any other exchange that will give you your bitcoin gold after the fork?

Well it is a free coin. That is why everyone is hyped about this bitcoin gold. And I really think that it is a good thing. It is just a free money guys! Just like BCC. I didn't think that it will attain good price. It was once $1300 so grab the opportunity.

Just read the announcement of your wallet provider or exchanges, they will provide you with their directive on what to do before and after the fork. Next is to wait for their instructions on how to claim your Bitcoin Gold. Not everyone will be moving their funds on Oct 25 mostly already bought Bitcoin for the anticipation of free Bitcoin brought by Bitcoin Gold.

The 100% fool proof way to be sure you can claim your BitCoin Gold is to keep it in a wallet where you control your private keys through the fork ... Like a desktop wallet.  Don't keep it on an exchange unless the exchange has agreed to make your BitCoin Gold available to you.  A few exchanges did this for BitCoin Cash, but I'm not aware of any exchange doing this to BitCoin Gold.  I'm sure if an exchanges makes that announcement, it will get posted here.

The second most import thing to do, is after the fork, and after the BitCoin Gold Devs have made a wallet available, is move your Bitcoin away from the wallet where you held it during the split... Do this before you attempt to claim your BitCoin Gold.  The reason is that when dealing your private keys to claim Bitcoin Gold, you may inadvertently expose your private keys to malware, which would result in both your BTC and BTG being stolen.  Don't put both at risk.

Now that's what I think too. It's funny that everyone starts rushing about the forks too early without any clue, official releases etc. It's better to stay patient for five more days until final countdown started. People will start there so called panic sell and all the bitcoin dump drama will start. Hope to see some good dip so as to buy more of it, :-)

The general procedure for any fork is to move your BTC to a new wallet after the fork and import private keys or seed from the old wallet to a forked client installed on a separate machine - be very careful when you are installing new wallets, since there will be a lot of malware, so always verify the source.
Generally, people want to own BTC before the fork, so altcoins will fall in price, but then very quickly recover right after the fork.

As I understand it, if you are concerned about losing money because of no replay protection, as soon as the fork has occurred send your Bitcoin from its current address to another address that you hold. Then it's safe. If anything occurs to the previous address (e.g. you move out BTG) the BTC can't also be lost.