This is obviously a glorified domestic to which there is never a straightforward solution. You may claim to have "nothing to do with him" but that sounds far fetched - there is clearly "history" between the pair of you.
That, however, does not give him the right to damage your property, but the bottom line is proving beyond reasonable doubt that he did it. You mention his boss, however, it's quite possible that s/he may be very reluctant to become involved, especially if s/he has been dragged into your spat in the past.
Injunctions are all very well but are merely temporary measures and this saga could quite easily last another nine years without satisfactory resolution.
I hate to advise anyone not to stay within the law in order to resolve their problems, but perhaps your ex would respond better to some "words of advice" from those physically able to stand up to him - if you get my drift?