Do you have the standard by-law about not smoking on common property?
And has the tenant registered the change of use of the garage from a place for parking a car to a retail outlet (or whatever it is he uses it for). Somewhere deep in the Local Government Act it defines a garage as a place for storing a car – anything else is a change of use.
A Notice To Comply about the smoking and a call to the council about the change of use might stir things up a bit.
But I’m afraid your concerns about the door sound a wee bit like clutching at straws.
By the way, if your strata committee refuses to do anything about by-law breaches (or does nothing about a legitimate complaint withing two months) you can take them to the tribunal and force them to do something.