What do you mean by lowering devotion? Devotion is at the max until you've devoted yourself to someone, then it will go down if you do something naughty to someone except for your selected love interest. If it reaches 0 - game over.
For Viktor you'll have to finish his quest - make Ms.Pierce move in, for this you need to raise her relations two times and then ask her out for Viktor, then after getting details from the date wait for some time. If she has already moved in - you gonna need to catch Viktor at kitchen drinking tea when you're wearing something that reveals breasts.
For Arty you need to make him catch you showering when he's at home and then let him watch.