This is a tricky question. If it is a unionized employment environment, then you 100% stuck with using the union grievance process as a means to get the Policy. You would not be able to do your own lawsuit.
In a non-union situation you could actually sue for something like this. It would be simply and straight forward in that you are asking the judge for an injunction or order for the employer to produce the document. You would be saying they are violating the employment agreement and duty of good faith as the employer.
I have to believe though that you could achieve the same ends by filing a complaint with the labour board. I have not looked into this but off the top of my head that is where I would start. The employer would be breaching its duty of good faith.
I believe you had the favourable insurance act clause that requires the insurer to produce the policy. Beware that the employer may be able to use this to say, you have the legal right to get the policy from the insurance company.
On the first question, no they really don’t have an obligation to assist you other than filling in the Plan Sponsor / Employer report and providing other information necessary for processing of the claim.