If btc forks in November will there be a 3rd coin? and will btc core crash if a lot of pumpers and buyers of bitcoin cash?
Yes, if they fork BTC to a segwit-1MB and segwit-2MB in November there will be three bitcoins.
The second question... If there are enough buyers for BCC buying with their post-fork BTC, the price of BTC will go down and BCC will go up. The higher the price of BCC, the more incentive for miners to switch. If enough miners switch to BCC, BTC could end up dead in the water since it does not have a difficulty adjustment algorithm like BitcoinABC. Everything depends on what people buy and sell.
I expect both chains to be viable though.
"I expect both chains to be viable though" wink wink lol