Coming in very late on this one, tcherry, but just wanting to say that I think I understand the difficulties you are expressing.
My husband isn't retired quite yet but he is working from home and doing much less, so he is 'around all the time' and is quite capable of impulsive trips to the shops buying 'all the wrong things', tidying the cupboards etc etc. There has always been a lot of conflict in our relationship about almost anything from how to lay paving slabs in the garden to the time children should go to bed to where to go on holiday. With each of us working outside the home (me part-time) there seemed to be some space, now it feels as though there is none and a lot of the time it feels as though nothing can be discussed because it is going to lead to disagreement.
You didn't say what kind of unwell he is but that sounds to me like a very emotional reaction and very possibly emotional blackmail too! It can't help when you already feel torn.
We have had our moments of pondering separation and I have thought quite a bit about leaving but it's hard if you have nowhere to go (eg. somewhere to stay even temporarily where you can find some space for yourself) and I sometimes think we have stayed together because of the impossible tangle of separating after 30 years. Then again, sometimes we have nice times together and still appreciate things in common.
We all make our own decisions and each of our situations is different with push/pull factors for staying or going. Whatever you decide to do, I hope you are able to rest with the decision, it takes a lot of courage to approach these big life issues and there is no doubt that retirement is a real cliff edge moment in life. I really hope you find some peaceful way forward, all the best.