First of all thank you so much.... Alot of people seem to be playing this with their kids which honestly? Is awesome to hear!!!
As for your questions
1: unless stated otherwise in the card you can move and then use your ability, like with the hopper you could move 3 tiles, then leap on someone's head with it. With the exception of passive abilities or stuff like the wraiths countermeasures which are activated under special conditions. Abilities basically replace an attack action ^^
2: line of sight is from the center of your tile to the center of the attack tile.
You actually worded it better than me I might as well steal it for the rulebook