If I shared a policy insurance with one parent(not going to claim them) how do I go about the “Percentage questions”?

[MaryK4]

You are allowed to allocate the policies any way you want.  There are many examples in Publication 974, Premium Tax Credit PTC for reference.  

If you cannot agree on an allocation percentage with all taxpayers who are including enrolled individuals in a tax family, the allocation percentage for a particular taxpayer is equal to the number of individuals the taxpayer will include in their tax family for the tax year who were enrolled in the qualified health plan for which you are allocating policy amounts, divided by the total number of individuals enrolled in the plan.