You're right to acknowledge that your handouts and that shes never worked has probably contributed to her not seeing any issue with pursuing a life where she also doesn't work.
But you also mentioned earlier that you did all of what you did so that she could pursue whatever she wants ... and this is what she wants. So you have succeeded in her feeling able to pursue what she wants.
If you're going to devote your life to family and never work, to be fair to her, she seems to have chosen a very financially secure option. She's not choosing to be supported by someone lacking ambition or who will only ever keep her on the breadline (the two do not necessarily go hand in hand, hence separating the two).
I always think that education is never completely wasted. Just because the output isn't a job which correlates to it. As a SAHM she will be bringing lots of value to her children. Through her education she has developed herself and will likely be in a much more powerful position in terms of feeling able to manoeuvre in the world I imagine. It may actually have played a good part in the attraction of her to her partner.
You say your only issue with her choice of partner is his age. In which case think yourself very lucky indeed. You could have a SIL who treats your daughter terribly. Who isn't well matched. Who she doesnt really love. Who you do not have any chance to get on with. If its just age then there is no reason why you cannot get on with him.
You say the age gap is 16 years and its mad to me that PP have referred to him as an old man. He is 38. That is hardly an old man. She wants children and his age doesn't prevent that. Depending on the 22 year old there is plenty that they could have in common. Perhaps she is very intelligent and likes that he challenges her, that he is more secure, that he is more settled and stable than many her age etc? I have friends with similar age gaps who have very happy successful relationships. Been married for over a decade with children. One couple I know have built very successful businesses together. Yes there will be cultural references etc and also the reality that if they both die of old age she could find herself with a longer period without a spouse. But if he is the love of her life why would she mind that compared to having a partner who might live naturally longer but she wouldn't choose?
She also has the benefit of being able to, if she wants and can, pursue having children younger than many women these days feel able financially. And that means his age gap will be less of an issue. I.e. many couples of similar age now wait until their 30s so the dad would be much younger anyway.
I think you're being dramatic about the age thing and also above anything else you risk damaging your relationship with your daughter
In your shoes I would help her to receive proper legal advice before marriage if he wants a pre nup and to advise her about making sure she is set up well incase it goes tits up. But she's already being sensible in marrying him rather than doing all of what she plans as a SAHM without such, or similar, protection. I'd encourage her to keep her hand in - either study as she wanted to be an academic anyway or volunteer/work part time. But if she doesnt want to its her choice.
Your worries about him isolating her/clipping her independence i think are fair but unwarranted if what you're thinking about is control/coercion as if he was controlling it doubt he would be encouraging and paying for further study, being a SAHM seems to be what she actually wants, and you have only raised his age as an issue so clearly no signs of anything adverse else you'd have other concerns than age regarding him
Support her OP and keep communication positive. Then she will turn to you if it goes wrong and if it doesn't she could have a very happy life indeed.