2 checked bags is not unreasonable for a 5.5 month trip. Paperwork will be the most helpful, and they will probably want to inspect your bags. They may raise slight suspicions, but in all honesty, the fact that you have an outstanding application will probably work to your advantage. Many officers have mentioned to me that it works positively for me because you want to be on your best behavior so as to not risk jeopardizing your pending application.
Proof of your outbound application is not necessary IMO... I've flown and driven into Canada twice since I got SA, (I cross the border A LOT) and both officers have mentioned my pending application, so they will definitely see it.
I would plan on customs/immigration taking some time, because your 165 day stay will arouse suspicions no matter what, but I wouldn't think it would be a problem with all the documentation you mentioned. My local immigration officers have mentioned to me in passing more than once (and I only mention this because we're both American) that once I have sponsorship approval I can actually ask for a temporary visitor permit for a year. As Americans without criminal records have very little that goes in the "what do they stand to gain?" column aside from being together with their family, the risk of overstaying (which is what the immigration officer is trying to measure) is very low.
