Gather The Townsfolk is one spell on the stack that generates multiple tokens. Each token entering the battlefield triggers a separate Cathars' Crusade "enters the battlefield" ability. (This is probably what that guy was talking about.)
However, all the tokens enter the battlefield simultaneously. The "enters the battlefield" abilities on the stack each resolve in turn, and all the tokens are already on the battlefield, so all the tokens will get a +1/+1 counter from the effect of each ability. This is clarified with the Cathars' Crusade ruling on gatherer:
The creature that entered the battlefield and caused the ability to trigger will also get a +1/+1 counter, provided it's still on the battlefield when the ability resolves.
The second part of your question.
And, if it is, what happens if, in response to the first or second token going on the stack, someone played a split second spell so nothing else could enter the stack (like the rest of the tokens)?
We've established that tokens aren't going on the stack, only the spell that creates them. They all enter the battlefield simultaneously, so there's nothing Split Second can do to prevent a token from being created. Split Second also doesn't prevent triggered abilities from going on the stack, so there's nothing it can do to prevent the tokens from receiving all the +1/+1 counters.