Landlord rights / security deposit

Question on security deposits and tenant/landlord conflict.

Where does one find out information about landlord rights, and to what extent we can withhold security deposits from tenant misuse of the property and its equipment, which results in material long-term damage?

Background: I own an apartment in HK, which has a very large patio. We have an awning over that patio which can be extended and retracted with a remote control. There are also some 20 floors above us which overlook the patio, and sadly every day some people above will throw some debris down. We rented the apartment out to a local HKer tenant. The tenant insisted in having the remote control to the awning, and stated he planned to extend the awning in a permanent/semi-permanent basis. We objected, because we felt that long-term extension of the awning could damage the awning arms and mechanism, and would potentially result in damage to the awning from debris from the above floors.

We came to a verbal agreement with the tenant that he would only extend the awning by 3 feet. Nine months have passed, and in our recent visit to the apartment we have seen that indeed the tenant permanently and fully extended the awning out to its full length, and that indeed this has caused the awning mechanism to be broken and non-functional.

What is our recourse? How can we document his malfeasance and what legal action can we take? Should we file a complaint with the Building Department? What can we do, as we now do need to withhold part of the security deposit to cover the damage caused to the awning mechanism? Thanks.

I believed you can both work this out.