A 234:
Also, they get another ability. It's like an improved Rapid Shot, except that it could be argued that it stacks.
It says that you can make 2 more attack and net -5 on all your attacks. It doesn't state that you can't combine this with Rapid Shot, you just need rapid shot to take it. So you could argue that by netting a -7 on your attack bonus you'll gain 3 more attacks.
Not really RAI I think, but it's RAW.
The last one is to give up attacks to increase the threat range of your arrows for a round. Trust me, not worth it.
-1 Attack for +1 critical increase?
No chance.