The Unbearable Lightness of Being, Bodies, and Nudity

I've recently finished this book. Overall, I enjoyed it but found it dragged at times and certain parts or ideas to be completely enigmatic or even nonsensical (more on this later).

Pushback on the concept of eternal recurrence and the "lightness" of existence. This is the central idea of the book and overall pretty profound and freeing if you can take it on board I think. This idea is hard to embrace in practice in your own life, as we're wired to feel existence is "heavy" or significant. While each moment may be fleeting and momentary, the embarrassment, shame, or pain I feel in a given moment feels very real to me. The consequences of this lightness idea are:

i) each moment occurs only once for an instant and then is gone forever. This part is both sad and freeing in some way. I picture each moment like a balloon floating away, kind of an obvious metaphor but it conveys "lightness".

ii) to put it in modern language, there is no way to A/B test or clinical trial your decisions and know if they are right or wrong, so you never know what life could have been like had you done a given moment differently

iii) if you can truly embrace this notion, then it's freeing because existence is light, momentary, and gone and therefore you can just "live in the moment"

I'm not clear how this idea tied to a lot of the goings on in the story. Tomas was, apparently, supposed to be the "light" character but it wasn't clear he was. Sure, he slept with a lot of women, and put his love, Tereza, through a lot of pain due to his continued infidelity, but he struggled with that and these two conflicting draws in his life. I guess I'm not sure how that's light. He came off a bit selfish and callous to me.

Probably the biggest mystery to me was the significance of all the "body" stuff, the idea that Tereza's mother had this bizarre belief she had attempted to ingrain in her daughter that "all bodies are alike, your body is not special and therefore you have no right to feel protective, possessive, or demure about it" (paraphrasing). I feel like at times authors come up with some idea, not uncommon with male authors trying to write women, where the psychological underpinnings of the character are so unbelievable that no such person exists or has ever existed in the entirety of human history. The idea that there is a woman forbidding her daughter any privacy even among strangers due to her belief that bodies are just bodies and you have no right to feel your body is special strikes me as absurd. If there's a deeper metaphor here meant to add something to the story, I am missing it.