ALS is great, when it's used appropriately.
This is an excellent situation that our (ALS-Only) Service beats into our heads, patients who are critically-ill, and this patient was, as soon as you saw respiratory distress.
Granted, now that CPAP is BLS everywhere (is there anyone reading this where their state is CPAP is only ALS?), it's possible that something like this could have gone BLS, if no ALS was closely available, but that shouldn't be an easy choice to make.
I don't believe this was accelerated junctional, at 164, it sounds like a rhythm that worked its way to a lethal one that should have been managed.
Bicarb was likely given, because the medics were just freaking out, or don't really know much science, or as you mentioned with the low potassium, the confused that with High Potassium, which is absurd, but not unthinkable that freaking out providers would confuse the two.
The reality is, this patient, prior to extrication, needed CPAP, a 12 lead, and (capable) pharmacological rhythm management, I didn't see much along the lines of medical history, I may have overlooked it, but without a significant cardiac history, the patient probably also needed IM Epi, and breathing treatments on top of the CPAP (which is probably a BLS skill in your state, but I obviously can't say that for sure, because I don't know where you are), Fluids and Mag (like I said, I don't know much about the medical history, so that blanket respiratory distress would need to be catered to this specific patient)
The old mentality of "everyone need diesel fuel RIGHT NOW" is wrong, that's true to traumas, but sick medicals, need time on scene, with effort put into it. This has been proven in studies, and when we implemented it in the field where I work, the amount of cardiac arrests we've had in our care was literally cut by 60%. So, your theory of doing nothing, and just driving, while it COULD be appropriate in some situations, is lethal in quite a few others, and there's now science to back that up, as opposed to how someone "feels". This call supports this statement. Short scene times are not always your best friend.
As for the code of silence, there is none. I don't care "how it works" where you are. There is none. This patient was improperly managed, it led to his death, there is no code. That's one of the few things I write people up for on calls. Shame on them, and shame on you for not going above their heads on this after the call. I do agree, once ALS care has taken over, your hands are tied, because if you say anything too contrary on scene, you could create a hostile scene (which is an awful mentality on the medics' part), but once the call is over, this call needed a serious QA by management, and I have a feeling that likely didn't happen on this one.
This sounded like a catastrophe all around, and maybe it couldn't have been avoided, but no one can say that, because no one practiced to their full scope. Basically, this call was a bunch of ambulance drivers, and I bet everyone on this call would be the first to be all up in arms about being calls that, even when that's what they've proven themselves to be, and it's embarassing to the profession.