does the second ability on meat eater stack with itself. the wording suggests no but i might as well ask.

as in if i use it once itll be one but if i use again will it pay for 2 or still just 1

It isnt worded as being the first momentum, so i would say you could respond with multiple meat eaters, each one counting as 1 momentum all ready used. Cards like Pirate Raid specifically state the "first" momentum.

the momentum replacement?

yes, each one will 'pay' for 1