It seems that the 75% rule may now me achievable, but there are a number of additional steps required. Most importantly, there has to be an actual redevelopment offer on the table. So you cannot be forced out because the other owner is planning to sell to a developer – there must be an actual deal in place. If it is a sham deal that the owner has concocted to get control of the premises, the Court should be able to detect that, and it would not be approved.
That deal must be fair, having regard to a wide range of factors, including costs you may incur in relocating. You will be able to object if you regard it as unfair, and the arbitration process is set out in the Act.
The process must have been conducted in good faith. In your case, I would guess that this requirement would be examined very carefully, because the 75% used to approve the action was held by associated persons. For instance, if the owner used their 75% voting power to increase your contributions or make other changes designed to force you out before the approval is completed, that could be taken as a clear indicator of bad faith, and the plan could be rejected.
If the other owner is able to come up with a plan that meets all those requirements and which makes it through the Court approval process, the likelihood is that the amount received for your unit will be considerably in excess of the current market value of the lot. That has been the experience to date.
There is free advice and advocacy available to certain people – you should check if you qualify:
https://www.fairtrading.nsw.gov.au/sites/ftw/Tenants_and_home_owners/Strata_schemes/Collective_sale_and_renewal/Strata_Collective_Sale_Advocacy_Service.page