Ok I am gonna try to be neutral hear, mainly because I am after some good advice myself in a minute, so here goes....
The bottom line is, in a perfect world we would all just wish each other a good future after a break up and move on with our lives, but if someone is stuggling to get over a relationship, no matter how it ended in the first place..it can make people do things they would not normally do...its a way of trying to keep hold of something that we no longer have..no matter how insane it actually is.
But to that individual, the way they behave is not only a lifeline to that relationship in their minds but its also a way of 'dealing' with things. If for example your ex loves you still and the thought (which would only be natural) of you being with someone else..especially in clothing he loved...really makes him upset..by taking that specific clothing he is in his mind somehow keeping you away from other men..or at least from looking your best in front of other men.
It will, to anyone else, including yourself, seem irrational, and it probably is. But sometimes we need to see why people do the things they do before we can make head or tail of it. Once you understand it, you can address those issues and move forward.
It might seem a bad idea, but if you confront those issues in a calm way and appeal to his worries and manipulate hiw way of thinking..in a clever way..then things will return to a sense of norm.
It just depends how badly you want things to return to normal and how much you like him as a person...if not a partner.
Its too easy for people to just say "he is a nutter" life is not as simple as that, and you have asked a question for advice..not just to pass judgement in yout favour..haven't you? Hope this helps