She literally hits all fucking four to a T.

BigMan, I suggest you see a psychologist to obtain a professional opinion on what you and your children are dealing with. My concern is that the 4 behaviors described above are red flags for BPD (borderline personality disorder), which my exW has.

I caution that BPD is not something -- like chickenpox -- that a person either "has" or "doesn't have." Instead, it is a spectrum disorder, which means everyone occasionally exhibits all BPD traits to some degree (usually at a low level if the person is healthy). BPD traits are primitive defenses that, when used appropriately and in moderation, increase our chances of survival.

At issue, then, is not whether your ex-fiancée exhibits BPD traits. Of course she does. We all do. Rather, at issue is whether she exhibits those traits at a strong and persistent level (i.e., is on the upper end of the BPD spectrum).

Importantly, I'm not suggesting your ex-fiancée has full-blown BPD. Only a professional can determine that. Instead, I'm suggesting you consider whether she may be a person with many strong BPD symptoms (i.e., may be a "pwBPD").

I’ve been steadily abused by my now ex-fiancée.

If your ex-fiancée is a pwBPD, BigMan, she carries much anger inside from early childhood. You therefore don't have to do a thing to CREATE the anger. Rather, you only have to do or say some minor thing that triggers a release of anger that is already there. This is why a pwBPD can burst into a rage in only a few seconds.

Moreover, the key defining characteristic of BPD is the inability to regulate one's own emotions, resulting in unstable behavior. This is why, outside the USA, most countries call this disorder "emotionally unstable personality disorder" (EUPD).

She has slapped me multiple times.

A substantial share of pwBPD never physically abuse their partners. Many of them do, however. This is why more than 30 empirical studies have found the physical abuse of a spouse or partner to be strongly associated with BPD.

And this is why "Intense, inappropriate anger" is one of the 9 defining traits for BPD. Indeed, the terms "anger," "impulsive behavior," and "unstable" appear in 4 of the 9 BPD Symptoms.

I miss and love my ex-fiancée.

If she is a pwBPD, she likely loves you too, BigMan. An untreated pwBPD is capable of loving you very intensely -- but it is the very immature type of love you see in young children. This means she will occasionally flip -- in only seconds -- from Jekyll (adoring you) to Hyde (devaluing or hating you). And a few hours or days later, she can flip back again just as quickly. These rapid flips arise from a primitive defense called "black-white thinking."

Like a young child, a pwBPD never had an opportunity to learn the emotional skills needed to handle two strong conflicting feelings (e.g., love and hate) at the same time. This means she has great difficulty tolerating ambiguities, uncertainties, and the other gray areas of close interpersonal relationships. She thus will subconsciously split off the conflicting feeling, putting it far out of reach of her conscious mind.

With young children, this "splitting" is evident when the child will adore Daddy while he's bringing out the toys but, in only a few seconds, will flip to hating Daddy when he takes one toy away. Importantly, this behavior does not mean that the child has stopped loving Daddy. Rather, it means that her conscious mind is temporarily out of touch with those loving feelings.

Similarly, a pwBPD will categorize everyone close to her as "all good" ("with me") or "all bad" ("against me"). And she will recategorize someone from one polar extreme to the other -- in just seconds -- based solely on a minor comment or action. This B-W thinking also will be evident in her frequent use of all-or-nothing expressions such as "You NEVER..." and "You ALWAYS...."

I cannot mentally handle it anymore.

Again, I suggest you see a psychologist -- for a visit or two all by yourself -- to obtain a candid professional opinion on what you and your kids are dealing with. Whenever strong BPD warning signs are appearing, it is important to see your own psychologist, i.e., one who has not treated or seen your GF.

In that way, BigMan, you're ensured that the psychologist is ethically bound to protect YOUR best interests, not hers. I mention this because therapists generally are loath to tell a high-functioning pwBPD the name of her disorder. They often decide that it is not in her best interests to be told.

Of course, learning to spot BPD warning signs will not enable you to diagnose her issues. Although strong BPD symptoms are easy to spot, only a professional can determine whether they are so severe and persistent as to constitute a full-blown disorder.

Yet, like learning warning signs for a stroke or heart attack, learning those for BPD may help you avoid a very painful situation -- and can help you decide when professional guidance is needed. I therefore suggest you take a quick look at my list of 18 BPD Warning Signs to see if most sound very familiar. If so and you have questions, BigMan, I would be glad to discuss them with you.