I dont think the dh objects to her having surgery.
I think he objects to her being a lump sum to 'improve her life' and views this money as purely hers to decide what to do with. Which is her attitude to marriage and what's hers.
It might be the straw that broke the camels back.
The isauea with the training is different to the surgery. The family are living hand to mouth. He has expressed he wants her to go back to work to help finances.
OP, has decides to invest this in fees to retrain. Not towards living costs.
So her husband, who she says is under stress now, will have to remain in that position while she decides what she wants to do and then does it. You could be talking 4 years.
She wonr even consider spending the money on making the family finances better, take the pressure off her husband and then look at what options they have with more financial room to manoeuvre.
She also doesnt see her potential inheritance as anything to do with him either.
So she gets luxuries. Being able to retrain when you have kids is a luxury. So is cosmetic surgery. So is a second car.
She gets luxuries, while no one else does. Because eventiay, at some point t in the future she might be able to contribute to family finances.
But then will she see that money as her own too?
The father hasn't offered to pay for education and surgery. He is giving her a lump sum to help her out. She has decided that its going on these 2 things.
Surely making family finances more secure would also help her out. Surely her helping relieve some pressure on her dh would be a priority.
Given the OP doesnt care if her and hee child live in a box to have this surgery, I would suggest she isnt thinking clearly at all.
It sounds like the surgery is a good idea and will help her.
But I think her attitude is off. And a man in her position would not be given any sympathy for wanting to spend money on surgery and retraining when his wife is the sole earner and they are struggling with money and his wife is unseen stress. Especially, while he gives the 'I am a sahp, we have joint money. Apart from anything that's mine. Thata not joint money'