What's up with my Minecraft textures?

Can't upload any pictures for some reason, but believe me, it's pretty bad. All of the mobs, at some point in my session, with develop a strange case of leprosy/gangrene and lose most of their limbs. Cows with have one leg and a head, sheep'll have just two legs, zombies will be just a head, I'll have a blue head and arm and nothing else, you get the point. Also, everything is extremely stuttery. Almost every time I turn, everything on the screen will flash and, well, stutter, and when I activate a piston (or pistons), they'll stutter too. My drivers are up-to-date, I just yesterday downloaded the newest version of Java, and, as someone said somewhere, I turned off mipmapping. None of it worked. My game is heavily modded (184 mods, FTB Monster v1.1.0). If you care for some reason, I have a Gigabyte 770 Windforce 4gb, and an i7 4770k. Sometimes, when I pan around above ground, I see what looks like a 2D blue whale. None of this happens on vanilla (1.7.5, at least), so is it a problem with the modpack? Should I try a different one, or update Monster? The only reason I haven't thus far is because my internet is terrible. This is really getting on my nerves, and I would love for this problem to be solved.