I think there are separate issues at play here but they may be feeding into each other.
The porn:
His watching porn of teenager, that is enough to make many uncomfortable even more so when you have a DD nearing the age.
I would personally feel wrong watching teenboys doing anything sexual but I do know it's a big kink area for some.
Being a turn off- if you feel you are compared or your husband is preferring these women to you it is very normal to not want sex. Add in if you dislike porn and it's even more so.
You need to speak to him about it and explain how you feel, how I or anyone else woud feel does not mater you just must be clear on how you feel and what you want when it comes to this.
Not everyone watches porn, different stroke for different folks.
Some women do and don't and same for men.
Some people don't even really get sexual urges at all.
Sex in general:
In terms of sex, before the porn watching (that you knew of), do you think you both view sex very differently?
You also say 'weird positions' (i get the anal thing) and I wonder if combined with the loving and tender that you aren't both very different sexually, both with different things that make you horny.
You say you want loving and tender, which is completely your perrogative to and no one should make you do anything you are uncomfortable with, but I must admit with my ex (few times back), he had the same thoughts and it really cause issues for us in the bedroom.
Sex was loving, never fucking, always missionary with occasional on top and he found the idea of anything like doggy very slutty-which was upsetting to me as I loved it and felt like he was calling me slutty or even perverse because I loved spanking and anal.
As a result, I didn't want sex with him as much. I got my thrills from reading and writing erotica and in the end we broke up.
We had not much compatibility and didn't communicate it at all (especially on my side).
Yes you must talk about the porn especially.
In the 70s some men were openly abusing young girls and it was laughed off so they didn't need to any porn.
Especially if they were rich and famous.
There was a big culture of it being okay to mess around with teens, just look at tv shows like 'it used to be alright in the 70s' you see them leeching over them.