Okay, first off, I only have my masters in clinical psychology so I'm far from an expert in either BPD or bipolar, and my replies are based on my limited knowledge/experience. Now on to your post....
BPDs are reacting to the world as they experienced it in a world everyone knows of. SZ-As are reacting to a changing world. They are experiencing a change in physiology that manifesting itself at the interphase of the mind and the physical world. Some ideas stay in, others creep outside. BPD is strong internalization of the outside - not the externalizing of the inside. I'm trying to describe what I "got" from your reply.
I have a little difficulty understanding this, but by "internalization of the outside" do you mean to suggest that BPD patients' issues with self/emotion regulation stem from things that happened to them in the real world? That environmental factors are more important in BPD, as opposed to the importance of biological factors (your reference to "physiology") at the root of schizoaffective disorder? If so, we're mostly in agreement.
Everything is taken real personally in BPD??? e.g. they pick up on the smallest negative expressions and let it blow up into a profanity (with everyone and all the time). It sounds like anxiety.
If that is a question, then the answer is yes. When you have difficulty regulating your "self" then it keeps popping up in social relations, communications, fantasies, etc. To protect the "self" you feel the need to be extremely alert.
And yes, you are right, anxiety plays a major part in all of this. Hence, a seemingly innocent but critical comment about ther person's appearance may be seen as rejection of the person and indication of future abandonment, which produces great anxiety. Unlike someone with dependent personality disorder, the person with BPD may react to signs of pending abandonment with fury and rage (and "profanity"). People with BPD have trouble regulating their emotion and their rage may alienate their partner--which is not exactly the end result that they wanted. It would help if the partners knew that often enough tremendous anxiety and fear is what drives the person's temper issues.
Now I might be making an unjustified leap... So if the outside is internalized it can cause euphoria or suicide - depending on where they are in life.
Not quite sure what you mean but suicidal gestures are quite frequent in BPD population.
What if a BPD person reacts best to a med not indicated for BPD. E.g. chemically there is no argument for it's use in this illness yet it helps in treating unwanted behavior from the patient's perspective. Are pills and skittles filling the emptiness/abandonment issue?
Forgive me if this is tedious for you.
There are no medications that can take away BPD in its entirety. Some meds like antidepressants can ameliorate the symptoms. Of course if the patient does very well on a mood stabilizer such as lithium, the doctor may suspect that the patient has bipolar disorder instead of BPD. In any case, usually psychotherapy (mentalization, DBT, various cognitive therapies, etc) is recommended in addition or instead of medication. But I digress. Medications and therapies help manage the disorder but not cure it. Therefore, pills do not fill the "emptiness/abandonment issue." However, this does not mean there is no hope. Patients do improve with appropriate therapy and/or medication. People with BPD also improve as they get older. Having a supportive and stable partner, family, and friends helps as well. Having a purpose in life and committing oneself to a particular path can also benefit the person.