Just want to clarify the issue of the work permit - being issued an open work permit after first stage approval is part of the
inland application process. If you file outland, which is still your best option (I'll explain more in a bit), the only option for a work permit is to apply for a restricted work permit . . . a relatively complicated process that requires you to be sponsored by an employer who has a job that has been HSRDC approved for hiring a foreign national. By the time you get that, you'll be approved for PR on an outland ap anyway.
Now, the explanation - first stage approval on an inland application takes (currently) 4-5 months, and then you will wait another 6-12 months for final approval and your PR visa. An outland application, processed through Buffalo, takes anywhere from 3-9 months to be finalized (plus about a month on the starting end for sponsorship approval) . . . in other words, permanent status in Canada and your ability to get a job without a work permit, as well as health benefits, etc. Besides that, the inland process doesn't have the right of appeal, and you can't risk leaving Canada during the whole process (up to 18 months) because, if you aren't readmitted, your inland ap is forfeited.
You can stay in Canada while the outland ap is processing - just be sure you
apply to extend your temporary status using this application BEFORE your six months original entry expires. If you get the ap to CIC before your status expires, you have implied legal status until they make a decision - so you don't have to leave. Be sure you include with your extension ap a copy of your marriage licence and proof that you have a PR ap in process.
Oh, and BTW, you can absolutely get your medical done in Canada - it
is way cheaper! Just be sure you take the Appendix D from the
USA Regional Specific Forms with you to the DMP and let them know your file will be processed through Buffalo, not inland Canada. Sometimes they assume, because you're in Canada, you will be filing an inland ap and they have been known to be confused about that. Just stick to your guns - the bottom line is that the results go to the same place (for US applicants) regardless of whether you're filing inland or outland - the DMP sends them to the Regional Medical Centre in Ottawa and Buffalo will request them from there when they're ready to review them.
Edit: I forgot - as far as traveling back and forth . . . if you file outland, you can do that without it affecting the processing of your PR application, but having a PR ap in process does not guarantee that you will be readmitted to Canada on your return. You still have to prove that you are admissible as a temporary resident. If you file inland the same goes - except that if you are refused re-entry, your inland ap goes down the tubes and you have to reapply outland.