Personally, I'd worry about FI first.
Once you get there, you can decide what to do with it.
I understand that but for me, it's important to know why I'm sacrificing to get to FI. If I'm white knuckling it through a job that is $$$ but miserable, I can do that if I see the light at the end of the tunnel. If there's no light then I should back down and get a lower stress/lower paying job.
Since your SO is on board with savings and
some investing (it sounds like) can you just hang on to that knowledge for a while (ie. what you are sacrificing) and try again on the ER for you in a few years? Maybe you can practice essentially living on your SO's income without them even knowing?
My DH has no interest in either of us retiring early but he is in his dream job that he wants to work until he is 70 and I'm in my love/hate $$$ job that I've been working for a decade to support him in his quest for his dream job. I'm waiting until our both our kids are out of daycare until I bring up ER for me again.
Sometimes people can't see beyond their immediate financial situation. My DH sees that we are saving lots of money, but he also sees that we spending lots of money on childcare. In 3 more years we get almost 2k back a month compared to what we have now. I'm planning on letting him see how much we accumulate at that point/already have saved towards my retirement before I broach the topic of me cutting back again.
In 3 years we should be able to live off of DH's income quite easily while letting my substantial retirement savings grow until we are old enough to draw it down. Can you give it a year or two and attempt something similar?