Depending on how the fibers are arranged and the angle and size of the blade, he could definitely be weaker against stabbing or slashing attacks. Anything that goes with the grain would be able to penetrate easier than anything going against it, but if there's several layers woven in a lattice-work pattern on top of the actual muscle fibers it would more or less become a moot point, since the fibers would be interwoven and at right angles to each other, making it impossible to slash/stab along the grain.

Since he didn't specify the use of a lattice pattern in the body's construction, it is assumed that no such layer exists and the body merely has the muscle fibers covered by his armor plating.

As to the effect of the net, I would also say that it would weaken/slow him, but that's because of my own theories on magic and how it works in relation to the observable universe.