Have individual insurance. Hit my OOPM. Living with partner recently. Want to add them. How does this change my OOPM for procedures done before they’re added?

So the basic facts of my insurance:

All USD – Ohio

Reference: Individual In-network / Out of Network ||| With Partner In-Network / Out of Network

Weekly premium: 50 ||| UNK

Deductible: 600 / 1,200 ||| 1,800 / 3,600

OOPM: 3,000 / 6,000 ||| 6000 / 12,000

So I’ve hit my OOPM for the year and am having brain surgery in a few weeks (September). Basically I become unexpectedly very ill this year. Like out of nowhere.

I want to add my partner as a domestic partner… Which we qualify for in October (6 months after move in). They have no insurance right now. I haven’t told them this might be a possibility because of this question.

How will this affect my OOPM and charges from before they’re added to my policy? Like I understand anything after is subject to the new terms… But I feel like I’m in a weird mystery gap.

I can’t afford to suddenly take on an additional 3,000 in debt to the hospital. With any luck this surgery fixes my brain almost entirely and there’s just normal follow ups.

So if I have the surgery now when I’ve hit my OOPM, and then add them when we qualify, does my OPPM get backdated to before they were added?

This isn’t some attempt to work around the system or anything. I could show our lease paperwork if someone was like ‘hijinx!’ I just want to figure out if I’m proposing adding them to my plan or not… Or waiting until the new year/elections.