I'm not a doctor, so I can't give advice.
If your Dad is waking up every 10 minutes, he probably has either sleep apnea or hypoxemia. He should be evaluated at the hospital for both, and have a BiPAP or APAP fitted to him.
No one should go from a MG crisis and being intubated to having nothing! He is not fully recovered. He needs a breathing apparatus ASAP (as soon as possible).
I can't advise you on the plasmapheresis. More than likely he will continue to need this done. Trust the doctors to handle that. But if they don't give him more plasma treatments, ask for more.
What other medications is he on?
I know how hard this is, to watch your dad go through such a hard time. But kudos to you for being his patient advocate! He needs one. I hope he continues to be better.
Annie