I get why your DH might have reservations.
The risks of something going wrong via general anaesthetic and him being a solo parent and widow....or it going horribly wrong and you looking like Simon Cowell.
Especially since you say you otherwise keep yourself 'natural looking', no fake eyelash, fake nails etc. Your DH might like the natural look, including your eye bags that come with aging.
There's also the differing values, he thinks it's superficial, you think it's important.
Ive had work done when much younger, and as I've matured it's made me realise it's not worth it. Sure it's nice to look good, but looking good shouldn't be the foundation on which feeling good is built. Working on your self esteem via therapy etc is key. Undoing societal pressures to look a certain way and knowing personality is key is essential.
Honestly, look into temporary measures eg fillers, serums, etc. Invest in therapy to address this. If you're still unhappy, get it done.
Your DH sounds like a financially controlling man. He is basically threatening you with poverty (relying solely on your low wage because you do the childcare)....if he can't dictate the way joint money is spent. King of the castle: Freedom project...look it up.
The fact he doesn't even want to discuss it is concerning. It's like he can't even be bothered to explain to you why he objects, as if you're not worth an explanation or discussion, as to why he disagrees. Again, red flag for an abusive man.
I bet he is controlling on other areas too.