To answer your questions:
a) and b) Proxies are not used at strata committee meetings. Instead, with the approval of the committee, another owner – including someone who is already on the committee – can speak and vote as an acting member. Same-same but different.
c) Acting members can’t be used to make up the quorum as their status has to be approved by the committee and the quorum has to be established before the committee can vote.
In the scenario you describe, the meeting would be invalid, as would any decisions taken at it (or at least they’d be subject to challenge).