Canadian RN student - OPT now, TN later?

Hi all! I've done a lot of research on this site and everything has been really helpful.:wink2:

I am a Canadian citizen (born&raised, passport holder), I have a BA from a Canadian university and I am an F-1 student in a post-Bachelors accelerated RN program in CT. I am graduating on Dec 7, and I have just started the application process for OPT. I am starting to think I waited too long -- my international advisor told me that processing times from the date USCIS receives my documents to when I have my EAD in hand is currently 5 MONTHS!! I plan to take the NCLEX in late Dec or early Jan.

A few questions:

1) My OPT approval from USCIS (i.e. my EAD) will probably still be pending during the holiday season. If I leave the US to visit family in Canada in December/January, can I still re-enter the US on my F-1? I am unclear about how the 60-day-rule would affect this (i.e. if I leave the US during this time while I am waiting for my EAD to be approved, can I get back in the country?)

2) Once I take the NCLEX, pass it and get my license (early Jan), I will probably not yet have my EAD. But, from my understanding I could then submit my VisaScreen and look for an employer, so I could then get my TN visa. Is it legal for me to pursue getting my TN while I am in the process of getting an EAD? How long does it take for a US-trained foreign grad to get the VisaScreen?

3) In your honest opinion, when should I expect to be able to work? February? March? OPT paperwork will be submitted this week. VisaScreen won't be submitted until probably early to mid January after I pass NCLEX.

THANK YOU SO MUCH!!!!

-H