For a psychological abstract, how long is too long?

Your paper probably has one overarching thesis, right? Your abstract should address that, not necssarily each of the components of the paper.

That said, I think 216 words is just fine.

This is my thesis:

“The diagnosis of ‘sexual addiction’ can be wholly valid, but it is too frequently applied unnecessarily to individuals whose sex drive is merely higher than societal standards find acceptable, perpetuating a sex-negative attitude and becoming a source of sexual shame. It would be beneficial to incorporate sex-positive attitudes into the discourse regarding sexual addiction, not only in terms of diagnosis and treatment, but also in the education of the mainstream public.”

The rest of the abstract does refer to specific points within the thesis, but those points refer to the sections and topics of discussion within the paper, so, best of both worlds, I suppose?

“How strictly should one follow guidelines like that in APA formatted psychological papers?”

If you want to be taken seriously by the establishment, then get with the established program.

The review could be listed as referenced footnotes or an addendum. It’s not your responsibility to offer a “review” to professionals. In fact, that only closes doors to those who would not agree with your review.

Your own ideas should come at the very end of the paper. Stick with the science for the paper.

I think you can shoot for 150; what happens is you´re excited about it, because it´s your article, so obviously it´s harder to summarize when you´re more involved in it. But that´s what proofreading is for, so as you revise it again and again you´ll find ways to cut down on it.
I agree that the thesis statement should be the focus. To me, it seems that it probably is the following one: benefits of working to incorporate attitudes that are more sex-positive when considering the varied sexual interests, in type/frequency/degree of intensity/choice of partner/etc., of an individual to alleviate the stress and anxiety the comes with socially-induced sexual shame and the stigma associated with sex drives on both frequency extremes (hyper- and hyposexuality);

One part you could eliminate are: “literature on sexual addiction” that´s a given, that you always include available literature on the topic when writing a paper, so you can cut that reference out, in my opinion
I think that the information about the DSM is just additional information, too, and can be extremely briefly mentioned, as an adjective clause (for example: the sexual addiction that has yet to be conclusively defined or included in the DSM-V) and thus does not take up a whole sentence or two sentences, but just a few words.

The reason why I say to shoot for 150 is 1) that people might not read much more, anyway, and you are shooting for getting people´s attention. 2) “rules” like using 150 words are useful for creativity, much in the way that the piano only has a certain number of notes even though there are many more available in the universe. The limit of words encourages one to be creative enough to summarize something that will be better read by the public and will thus help them to quickly know what your article is about and hopefully will entice them to read it. Less is More.

Sorry, I noticed now that you had already written what your thesis was. But I grasped it anyway from the information you provided in the question.

Now I looked for information online, and this article sounded interesting: http://www.ece.cmu.edu/~koopman/essays/abstract.html
Whereas some links mentioned 150–250 words, the article I mention suggests 150–200.

Hi @TitsMcGhee! Welcome back! Great to see you!

I have to say that your paper is right on target for me and the issues I am struggling with. I even went to a number of SLAA meetings. The line you are talking about—between sex positivity and addiction seems like a difficult one to draw. At least, to those who don’t understand it. I think if you’ve ever been there, it’s clearer as to which side of the line you are on. Although, in my case, I think sometimes I’m on one side, and sometimes the other. There was a recent question about sex addiction here; you can see what people think.

I think your thesis statement would make a great abstract. What was your method? What were your findings? A sentence about each and you’re fine, I think.