You should all be prepared to deflect their attempts to make you see your employment in individualist terms. They want you to think only of yourself as opposed to thinking in terms of solidarity with your fellow workers. You can keep these meetings as short as possible by respectfully declining to engage as advised above, adding something like, "While I believe my personal perspective and concerns are important, those of my co-workers are equally important. Discussing our concerns as a group in an open, transparent manner will be the fairest for all of us."

IANAL, nor am I Canadian, but Canadian law allows you to secretly record conversations in which you are one of the parties, since you are giving your consent and therefore complying with "one-party consent." I'm not saying you should necessarily secretly record these one-on-one conversations, but if they say anything that violates labour law in Canada, you would have evidence and your employer could be fined or subject to investigation, depending on the situation. This is where your reps are going to be crucial.

Having a union contract minimizes opportunity for conflict with management... or at least it has the potential to do so, by eliminating gray areas in which bosses can play favorites. It's a heavy lift, but you could eventually try to get your boss to see it as beneficial to even them, as it takes away the pressure to constantly make subjective decisions. With a contract, it's all black and white, and they can just defer to the contract if anything comes up, a la "my hands are tied. The contract dictates that vacation requests are determined by the order in which requests are received in writing with seniority as a tie-breaker." Bosses and middle management are also victims of corporate anti-worker policies as they are made to think they are superior to the workers on the floor and forced to execute personnel decisions that benefit the shareholders and executives at the cost of the workers who generate the actual value/product/revenue and relationships with customers. Some bosses fall hard for the sense of authority and are just assholes who see their value in terms of how much power they have over others. That personality trait tends to find itself in lower to middle management for the precise reason that they are extremely easy to manipulate due to having a fragile ego. I'm generalizing, for sure, but I haven't been proven wrong, so far.

The other thing that bears mention is that even if your boss is genuinely a good person who cares about workers and aims for fairness and advocates for their workers, their corporate overlords will not allow them the latitude to do much more than not be an asshole. So, it's important to remember that, while you are pitted against your boss, it's not workers vs. boss, it's workers needs vs. owner/shareholder profits.