Your Calcium isn't too low. Ours is kept at around 450 and just raised when needed but it does stay very stable.

For your anemone, it will find somewhere it likes and stay put. As long as it gets everything it needs it will eventually stick to one place. A fellow reefer we get SPS frags from has a enourmous anemone, no joke it is over a 1ft wide, infact, probably bigger. He said it hasn't moved for around 15mths. But if it were to It would sting everything to pieces and totally wreck his tank. Its tentacles are around 7 or 8". Biggest one i've seen.