DUI cases are almost always more complex than they first appear. So in answer to your last question, if it is something that you can afford, retaining counsel in advance would be advisable. Additionally, you can anticipate being charged with a refusal, along with the underlying DUI charge.
You are correct that neither the Field Tests nor the sense of smell is an accurate measure of the per cent of alcohol. But along with the driving through the stop sign, they are all supportive of probable cause.
Depending upon the circumstances, a .08 or .09 may sometimes result in a wet reckless being negotiated. However, absent some very unusual circumstances, a dismissal or non-alcohol reckless is quite unlikely.
From your question, I am not exactly sure whether your upcoming appearance in January is your first appearance or not. If so, you may be expecting something to happen before the time that it actually can. There is not much that your attorney can do for you until that first appearance.
Yes, some people have been turned away for a prior DUI, which the Canadian Government apparently takes pretty seriously. It depends upon what they ask you, because some individuals have not been questioned and have gone right through. Some, in the face of being turned away due to a prior DUI, have been able to pay a $240.00 rehabilitation fee. It is apparently a bit dicey up at those border crossings!
You definitely do not want to go through this process without the advice and assistance of counsel. And whether it by an attorney that you have retained on your own, or by a public defender, if you qualify, based upon your low income, you definitely want an attorney representing you. To many individuals look back on trying what you are suggesting, and in retrospect, wish they had been represented. Don't find out after it is too late.
Here is the dilemma. State appointed attorneys are very often difficult to access or communicate with because of their heavy case load that ultimately pays them very little for each individual case. The minimal amount paid per case provides little incentive to do very much on each individual case. If getting paid minimally on a case diminishes incentive, how motivated do you think a Pro Bono attorney will be, given that they are being paid even less for your case than the state appointed...
In the situation you are describing, it is certainly possible that the amount of time that you could be looking at could be considerable, However, there may be ways of handling this that could get you through this with a very minimal amount of time. This is not something that you want to delay any longer! As you delay addressing the situation, the reasons that an attorney could present to explain the delay continue to diminish.