Ah, I think I see now.
From a custody perspective it would indeed be easier for you to wait until she is 18. Whatever worries about her part of the sponsorship application should mostly go away then, right? From reading the conversation, though, it does seem as though you are entitled to take her with you regardless. Unfortunately in Canada these types of decisions are at the discretion of the person making the decision on your application. Nobody really knows for sure whether or not your application will be approved until there is a decision.
As to the teaching thing: I have a hard time imagining that if your teacher's union in Texas sanctioned you for resigning improperly that this would keep you from working in Canada (provided of course your degrees are recognized here). I don't know what the mechanism would be for a Canadian provincial teachers union to recognize this. There might be one, of course, but it strikes me as unlikely. (If there's, say, an organization of North American teachers unions, they might have such a rule. I'm speculating.)
There's one other consideration here: inland vs outland. It sounds like you are considering inland: the two of you come to Canada as visitors and then he sponsors you once here. Do I have that right? The other option is that he sponsors you while you stay in the States and work. (Outland.)
I can't give you legal advice about this, as I am not lawyer or an RCIC. All I can say is what I would do in your situation. For me, I think I might try outland, applying some time after she's 18, working another year and then resigning next summer and "landing" (coming to Canada) when you've both been approve. That strikes me as the safest option, though is obviously not necessarily the more preferable in terms of time with your husband.