Bubbles – in response to your questions:
1) YES you can certainly pressure the Building Manager, but as they only work for and take instructions from your Owners Corporation (i.e. you), it would be better in my opinion for you to also write directly to the Secretary of your Executive Committee (cc Strata Manager) pointing out everything that you’ve mentioned in your post, and requesting that the matter be formally discussed and resolved at a Committee Meeting.
2) Strictly speaking, in the situation that you describe responsibility for and therefore the cost of repairs would be shared 80:20 between the Owners Corporation (O/C) and yourself, and ideally with repairs being undertaken by the O/C and the costs being shared upon completion of the works. If the O/C doesn’t mention the shared responsibility, then given the inconvenience that you’ve suffered to date I’d be inclined to let that pass.
3) Again strictly speaking, the O/C is only responsible for rectifying the fault and anything that is consequently damaged during that process, and the repair or replacement of your carpet is your responsibility and covered under your contents insurance (if you have it).
By “strictly speaking” I mean under a strict interpretation of the NSW Strata Schemes Management Act, however logic and goodwill (albeit measured given it’s been 3 years) may see a more amenable response from your perspective, which is why I haven’t trawled for any legal precedents – even though those may become relevant IF your Executive Committee doesn’t react in a timely way.