How “final” is the final custody order?

I live in Illinois. It has become abundantly clear that I will not get 50/50. It’s a long complicated story, but I don’t think it’s going to happen.

However, custody orders can be changed after 2 years and a substantial change of circumstances.”

The supposed presumption is 50/50 parenting time in Illinois, so how likely any I going to get 50/50 after the divorce is finalized when custody is reconfigured?

I’m asking because I’m wondering how hard I should fight for 50/50. The reason why I’m not getting it is complete bullshit (I live too far away (five miles) and I can’t get the kids to school on time (lies but the gal believes it). But I those conditions changed and the final parenting order says “dad moves within 3 miles” and mom agrees to it, do you ever get more time?

I assume mom is always going to object because she doesn’t want to pay child support, but anyone ever get their parenting time increased?