The metal barrel does not convey טומאה to the adjacent room (even though חרב הרי היא כחלל [even regarding אהל]), either because it is completely covered by the sticky dried figs, or because the barrel does not extend into the airspace of the adjacent room.
Attached plants cannot be an אהל (to bring or protect from טומאה), however they are effective in diminishing the size of an opening. A צמיד פתיל is required to save from טומאת אהל; however it is unnecessary when diminishing the טפח size of an opening.
And a Gentile who sat in the window - ועובד כוכבים שישב בחלון
A נכרי is not מקבל טומאה מה"ת, and therefore he can be חוצץ בפני הטומאה even though that מדרבנן he is considered a זב. A בן שמונה is neither totally alive nor totally dead. Therefore he is not מקבל טומאה.
Since there is suffering for an animal, etc. - כיון דאיכא צער בעלי חיים כולי
One would not be מבטל an unfit to eat (non-kosher) animal to the חלון; he will either use it for amusement (if possible) or throw it to the dogs; however he will be מבטל the אבר המדולדל of this animal to the חלון if the animal can entertain him.