1) Your assumption is incorrect. You do NOT have to apply Inland just because she's in Canada. For most cases, especially for Americans, Outland is faster, plus it preserves your right to appeal and your application is not jeopardised by travel out of the country if it becomes necessary. You can apply through Buffalo.
2) See above. However, yes, Inland applicants are recommended to remain in-country, as this is the basis on which their application is accepted at the processing office handling such cases, and if for any reason the applicant cannot return, the application is dead in the water.
3) See 1) above, again. However, yes, Inland can take as much as 18 months or more. For straightforward cases, many persons are getting first stage approval and PR together recently, so minimum of 10 months.
4) No, one status does not give priority over others in the processing of spousal cases. However, Buffalo is averaging 11 months for 80% of cases, although some Feb, Mar and Apr 2011 applicants are receiving PR already from that office (4-6 months).
5) If she has to go back and forth often, border officials MAY get testy. It is essential to have proof of her status (student ID etc) and of the spousal application in process when she travels (copy of receipt, copy of sponsor approval letter). It's not for certain they will hassle her, given she already has student status, but better safe to make no assumptions and be prepared.
Spousal applicants are exempt from the "excessive medical demand" clause, therefore your application cannot be denied on medical grounds.
6) As long as you are not an undischarged bankrupt, or in receipt of social assistance for reasons other than disability, financial matters do not impact your eligibility. With no legal proceedings, I cannot foresee this being an issue.
"He who asks a question is a fool for 5 minutes. He who never asks a question is a fool forever." - Chinese proverb. Ask away, that's why people are here, to help if they can.
P.S. A permanent resident is required to reside in Canada 730 days out of every 5 year period (on a rolling basis). Remember that when your wife has PR and you are off in Africa, so she doesn't run afoul of the residency requirement.