Rtd
PM,
Well, from my own experience, it definitely makes sense to use your NP, especially if you have one already. I took lots of considerations before renewing mine, hence the last minute renewal - I got mine renewed only 1 day before I travelled.
If you are a refugee, and your country doesn't have an embassy here in the US, it makes sense to obtain RTD since you can't get your passport renewed anyway. But you said you do have an NP. On top of that it sounds like you are really well prepared. You even got an email re. your parents' health etc. I really believe as long as we show them strong reasons for us to stay as a PR, we should be fine. You are going home to VISIT, not to stay there. If you start looking for a job, or buying a property there, and then you tell the US Immigration all this, then yes, I guarantee you, you'll have problems when applying for citizenship.
As long as the visit is reasonable, I truly believe the US Immigration will not give you any problem.
Just my 2c.