I know I can only take responsibility for my own actions and the things that are within my control.
Correct.
But you are not taking any action.
You've spent at least a month here (other threads) where you have not, it appears had a conversation or moved anything forwards.
I'm sorry but a 'health scare' and surgery are not reasons to behave as she is.
Was it suspected cancer? Did she have a biopsy or similar?
'Living for today' does not exclude saving for the future so you both have a comfortable retirement .
It does not mean she takes no role in contributing to finances.
And given she wants to be a good mum and homemaker, she's doing the exact opposite.
Because your younger daughter will know things are not right. She will feel the tension even if you are not bickering daily. Kids pick these things up.
Also she's setting a bad example to your daughters.
She's not showing resilience, determination, ambition. Mothers have a big impact on their daughter's futures and careers. The are role models.
She's living off you. She has no financial independence. She is stuck in a relationship which isn't making her or you happy.
IF she wanted to live for today she's be getting out. She'd not be wasting time on a relationship that appears to be over. She'd be retraining, or taking a job (assume she did have a job before she stopped work 20 years ago) .
You say you can change your behaviour - but are you?
Why are you not sitting down with her and saying -
'Look, we need to have a very serious talk about where we are and where our relationship is heading. I'm not happy, you're not happy,it's not right to inflict this stressful set up on our children.
We either work together - and that includes you getting some work as well as reining in your spending - or we split up.'