Same, just finished 4 last night. Books 3 and 4 were vastly, vastly better than the first one in all ways, especially the sex stuff. Don't get me wrong, I'm as vulgar as it gets, and I don't give a shit if they want to include that sort of thing, but it was mostly just dumb how it was handled. And makes it hard to recommend, as you mentioned. Also, I believe it was book 2 where it happened but I could be wrong, the way that Fizzy was "broken" was actually upsetting to me. Not in the way normal people get upset, because I basically just mentally cringed and then shrugged and moved on, but I'm sure anyone that has read it knows exactly what I am talking about. It was shitty and distasteful, and while I see how he got from point A to point B, and why he chose to do it that way, but it was still completely unnecessary. I would imagine that's the point at which some people on the fence about the series would hop off.
If he had just taken that part out entirely and left all the mental abuse in, it still would have worked just fine I think. And same with all the Book 1 sex shit. It needed to be set up a little bit for the rest of the series to work the way he wanted it to, I guess (I'm pretty sure the series would have been just fine without ANY of that stuff though), but he could have just implied most of it. Ignoring all of that shit, these were actually a highly fascinating look at the mind of a true monster. I'm glad that Boxxy has mostly remained the same, while still learning to temper his behavior to fit in, and that is what has kept me reading. But fuck, he should rewrite that first book, and parts of the second, if he ever hopes to get any kind of mainstream acceptance. I'm no prude, so it's whatever to me, but yeah, I'm never going to tell a female to read these books, that's for sure. Well, unless I hate them.
At least it appears I can happily look forward to future books if they maintain the same level of quality and self-censoring as this last one. That last book was a solid 4, maybe even 4.5, out of 5 stars. Which is saying a lot when I compare it to "legit" novels, because most of this litrpg stuff is immensely fun to me, but I can acknowledge that they are not at the same level as a lot of the other stuff I read.