What is the action of the Rectus Sheath?
And Linea Alba?

To protect the muscles and vessels.

Explanation:

The function of the rectus sheath is to protect the muscles and vessels which it encloses. In addition, keeping the rectus abdominis and pyramidalis muscle together helps in providing maximal compression of and support to abdominal viscera.

The function of the linea alba is to maintain the abdominal muscles at a certain proximity to each other. In the case of long-lasting increased intra-abdominal pressure, the linea alba widens.

if the hares very faster than they are now, and thus the lynx's hunting success rate drops because it will be harder to catch them, the rate that will change will be the pray-rate. the pray-rate will change because more hares will be able to survive, thus more individuals for reproduction, so the end result will be increasing population of hares.

the predator-rate will remain pretty much the same because there will be more than enough pray, but the hunting success rate is stagnant.