Dramatic Frames Drop

If this only happens in your one world, it will difficult for anyone to help you. FPS can lower based on many potential issues. Light is the most common, chunk loading is another. You could even have a virus. You'll have to do some testing and figure out what causes it.

it's entities or movement of the players, most likely, and my base is filled with chickens, villagers, item frames, and other entities, although only happens apon movement.

I can get upto 70 fps in this world only, and only this world lowers to 0 fps. Other worlds have 5-30 fps on average, depending on which type of world, sandstone test worlds are at 20-30, LP's are at (not this one though) 5-20, and default test are ranging from 5-25.

Stayed at about 20 in 14w11b or earlier.

Please force a crash by pressing F3 + C for 10 seconds while in-game and attach the crash report ([minecraft/crash-reports/crash-<DATE>-client.txt|http://hopper.minecraft.net/help/finding-minecraft-data-folder]) here.