Absolutely run it into the canister. You will get better diffusion that way. If you want to run a diffuser right underneath the intake, that would provide for better diffusion as you get micro bubbles going in. But that is personal preference. Just put the end of the tube in the intake.

To make your DIY last longer, use the Jell-O method. This helps "limit" the amount of sugar the yeast has access to. As the Jell-O breaks down, more sugars are released. When you see it starting to fall off (drop checkers are very helpful for this), just pour the water and recharge with a fresh batch of yeast. I've had bottles last for well over a month.