[Vince]

For one, your distance function seems to be completely wrong. Why are you raising to the power of 6? Check here for an easy GetDistanceBetweenPoints: https://sampwiki.blast.hk/wiki/VectorSize

Secondly, you're using DestroyDynamicMapIcon wrong. The iconid is not the same as the mapiconid and multiple mapicons may use iconid 31 (green house symbol).