Great description of your process, but several of your steps seem unnecessary to me based on what I have learned.
It is not necessary to wash and rinse the parts separately-the soap, hot water and rinsing remove the bacteria. Daily vinegar soaking is not needed if you are heating the pieces. One use towels - I am careful to not touch inside the parts and not worried that any minute amount of bacteria might migrate from outside to inside. Finally, if you are using two sets daily, you could rinse the first set and leave them in a bowl, then clean both sets at once. If you remove them from the water while it is still hot and shake off any drops they will be dry for the next use.

As for time to nebulize, Iuse the Pari eFlow Rapid, which takes under 10 minutes even when stopping to cough. Considering this is a lifetime commitment, it seemed prudent to my husband and me to do what was possible to make good use of my time. Even before that, I used a DeVilBiss Traveler, which took about 15-17 minutes.

All nebulizers are designed such that roughly 1ml of the solution is left behind in the bowl or mouthpiece so you don't get the full quantity into your lungs. Dosages are calculated with that in mind.

When it comes to saline, there is no "set" amount. You need enough to thin the mucus and get it moving. That can vary between individuals and for any person it might change from day to day.

Coughing while webbing is another individual thing. I was taught to try NOT to cough while ding the saline, but to wait until it penetrated then do deep breaths and huff coughs to get the mucus up.
Sorry to cut this short. On a road trip and it is my turn to drive.