Sorry for replying piece meal, but as I reread your post, I noticed:
"And in turn cause low potassium levels---but that would not explain the cause of the collapse. "
This could mean that the low potassium may NOT have been the cause of Terri's collapse.
One of the things I find odd, is that if a husband finds his wife face down, would any reasonable person leave her lying there that way, instead of turning her over and try to find out what's wrong? Unless he laid her down that way, to make it appear she collapsed while coming out of the bathroom. The paramedics found Terri face down.
This is what told me a lot!! When my father had a heart attack and I found him face down, the IMMEDIATE response was to turn him over. I think that may have well played into suspicion for the paramedics to call the police to the scene!! Think about it. WHy would it look to them like a possible homicide????
Especially a husband who knows CPR (wasn't he a respiratory therapist at the time?) He didn't even try CPR!! One would think that would be enough to jail him.