You are perfectly right that uncertainty and not knowing what to do and when to ask for help (and from who) leads to understandable anxiety and can definitely make breathing difficulties worse.

If you are experiencing breathing difficulties/have respiratory muscle involvement you need to have a respiratory consultation (preferably with a pulmonologist with a good understanding in neuromuscular diseases).

You can find (together with him) a parameter which is good to follow in your case.

I use a simple peak-flow meter when I am not sure what is going on. (It seldom happens now, as I have learned to recognize my symptoms fairly well, but I too am not always sure and in the earlier days of my illness I used it a lot).

I have found that for me there is a nearly 1:1 correlation between my peak flow and CO2 level. (CO2 is much more sensitive than pulseOx to changes in respiratory muscles, but it is not checked routinely).

I have made my own chart which goes from: able to breath normally, have slight difficulty breathing which only I notice but not those around me, have more significant breathing difficulties that is noticeable to others when I try to talk, having breathing difficulties that make it impossible to talk, hardly able to breath and becoming foggy-requiring respiratory support.

I have been able to correlate my peak flow numbers and CO2 levels down to hardly able to breath. Beyond that I was not able to perform the maneuver required (so can only guess what it is).

Having this chart helped me significantly in eventually learning how to recognize the different situations and in finding objective correlates (after all I am a physician and need some objective proofs sometimes). It also helped me monitor my response (or lack of response) to various treatment interventions.

I usually try to use my respirator before I reach the level of being foggy and most of the times I am able to recognize earlier signs. although, there have been times when I was no longer able to put on my respirator mask and required someone's assistance.

I can't tell you at what point you should go to the ER, because I personally never do (but I have a mini-ICU equipment at home, so don't need to).
We do follow my O2 sats, but only when I am experiencing breathing difficulties with my respirator and have significant swallowing difficulties which can potentially lead to airway obstruction .

I was only hospitalized during my first crisis after that I have learned learned how to manage it on my own.