Dr Phil said that separation does NO ONE any good as it just creates distance.
HOWEVER... if there is an AFFAIR going on, its the healthiest of two evils.
If you can get him to commit to NO CONTACTT with OW BEFORE you move in then I say go for it... besides, you can't keep an eye on him to make sure he's being honest if he has his own place, it just is a license to play... I don't understand why couples separate.. it's just silly...
I have anotehr video I will post up for you soon on this topic