A) Big. The south side alone is ~60% of the city; the west side is much smaller, but the point is that by land area (not a great measure, admittedly), there's just a ton of space to patrol.
B) No. It's been tried, pretty consistently, with (at best) mixed results. Under Rahm, at one point (may still be true), CPD was paying boatloads of money in overtime to saturate violent neighborhoods.
C) That said, the book Ghettoside makes the really convincing argument that neighborhoods like the ones under discussion in Chicago simultaneously suffer from under- and over-policing. There's a massive police presence in much of the south side, kinda, and a lot of people get arrested for a lot of stuff. At the same time, the murder clearance rate (the number of murders "solved" by the police) was ~17% in 2017 (https://chicago.suntimes.com/news/murder-clearance-rate-in-c...) but over 60% in the (rather more violent) 1990s. So a lot of people have a lot of negative interactions with police, but the most serious crimes - murder especially - rarely get solved. Lots of people in the neighborhood know (or suspect) who did it, but that person never goes to jail (for that crime), resentments build up, it becomes harder for police to cultivate good sources/relationships, retaliations occur, etc etc you can imagine how things go.
D) There have been pretty successful interventions; CeaseFire comes to mind (https://chicagodefender.com/2018/01/10/the-return-of-ceasefi...). But it's suffered from lack of money and infighting at the state level between Rs and Ds. The basic idea, though - intervene in violent situations with people who are from those neighborhoods and used to be in gangs - seems to work quite well. It just needs money.
E) Crime is still actually down when compared to the 70s/80s/90s. Not that that's much comfort to someone living in one of the affected neighborhoods. But the country as a whole has become both more peaceful and more media-saturated, so aberrations like this get much more attention and the problem seems worse than it is - though again, that doesn't mean much to someone who just had a loved one get shot.
