In order:

1. When you become half-farspawn, you continue losing sanity in the normal method. The thing is, however, that half-farspawn are not sane by nature. As such, you are merely getting closer to your natural mental state.

2. When under the effects of dimensional anchor or dimensional lock, you cannot use your spell-like abilities (you would be similarly stopped by anchor mist but you would not take damage unless the spell-like abilities themselves try to teleport you). Simply put, its a bit hard to pierce a microscopic hole into a place beyond all of existance, siphon some essence from beyond, and shape it into a spell when you have access to no planar travel at all.