You can actually leave the airlock off and cover with a sanitized cloth and it will work fine. You can keep an airlock on, and just remove it while you stir/aerate it each day then put it back on. Whatever makes you comfortable is okay.
Since you are aiming to keep it sweet and don't need to push the yeast to maximum alcohol tolerance to dry it out, you don't really have to do the staggered nutrients. You can add them all at once if you like.
It is hard to say how fast a fermentation will go. You really have to monitor it to know. Again, as you aren't pushing for maximum alcohol tolerance, if you just aerate it for the first couple of days, you'll be fine.
Flavor preference is tough to predict, but 2 pounds in a gallon will generally give a light berry character. 3 pounds will make it medium; 4 pounds will be strong.