I personally am partial to option 1. This is a variation of what my DH and I will be doing. But with some slight tweaks:
Save up as much as possible in the meantime to make the transition as smooth as possible. See if you can "live" on only your salary and bank his. Research the Rule of 72 (more below)
Plan for the worst case, that your partner never re-enters the workforce. It could happen, and you want to keep the household afloat if that does happen. But hope for the best, that eventually your partner does re-enter the workforce.
Perhaps, plan for your partner to begin re-training/certification while being a SAHP, and re-entering the workforce into this new industry as an entry level. And that would be fine, because his additional income is just a bonus.
For context, this is my DH and I's plan:
Save up $400-500k (currently $200k) and when we have our first baby, I can walk away happily and know I never *have* to work again. Be a SAHP for a few years, then possibly re-enter the workforce part-time after that. Maybe not necessarily in my original field, but it could be a possibility.
DH's salary would be enough to cover expenses with a bit left over. He could even drop down to a part-time salary and still cover our necessary expenses. The Rule of 72 states that if left alone, on average investments will DOUBLE during a decade. So, our $500k left alone, not even contributing another penny, will grow to $1 million in 10 years, which is our FI number. Anything extra beyond what is needed for our expenses (including any of my new part-time income) will go towards padding this stash, plus we would likely continue to work part time beyond that, especially while we are settled down and our children are in school. We would have ~$1 million when our oldest is 10 years old, and we have another 8 years to occupy ourselves before they would head off to college. Might as well fill the time with some income-generating work. Additionally, this is a good safety net for FIREing - if we hit a few bad investment years, we just simply continue working part time to at least partially cover our expenses (between the 2 of us, this should be doable) until things level back out and we are comfortable pulling the plug. By having one of us work at least 32 hrs/wk, we also get a few more years of being on employer health insurance and a 401k match.
It is quite possible that your partners anxiety may lesson when his exit is so close. It did for me -- I'm planning on leaving in 3 years and being a SAHP, and now when things pop up, my brain goes "I won't have to deal with this bullsh*t in 3 years!", and I'm able to give myself permission to take on less responsibility and stress. I'm not gunning for promotions or lateral moves or trying to impress my boss--the pressure is completely off, and I'm essentially just cruising until I leave.
DH and I came up with this plan last year, and until then I had been experiencing more and more anxiety and exhaustion. As soon as I had a firm-ish exit date, it melted away.
Additionally, it has taken some pressure off DH too, as he knows that as soon as we hit our pre-baby $ target, all he has to do is cover our (mustachian) expenses. So he doesn't feel the need to go crazy for promotions or work late or anything. He is actually planning on going down to 3/4 time for a few years, which would still be enough to cover expenses while our investments simply grow in the background.