I dont think it would be overkill but you will most likely have to run it at 70% or higher for that size tank. I would recommend a mp40 for anything larger than 50g, run it at 20% or less and if you ever decide to upgrade to something bigger you can move the 40 up with you.
I would blast your rock crevices and underside with a turkey baster so if there are any leftovers, they will float and your wrasses can pick at them better.
Couple of days, might be longer depending on if they like the water param or not. They can go days or weeks without having their polyps out but doesnt mean theyre dead, they just dont like something in the water.