Seems like the key chunk is the percentage of affected people who progress to needing ICU and/or vents, which is about 5% of all cases, definitely less than 10%, I believe. If early intervention with meds can cut the need for that level of care by a half or 2/3's, maybe we get just below the threshold that crashes the system. Maybe health care still gets swamped, but finding a way to curtail progression to pneumonia would go a long way to making a sustainable effort. Temporary hospitals in tents, hotels, boats etc can be set up in a reasonably quick manner and handle a lot of sick people. Even though it's that critical need for ICU's/vents that really grabs headlines, the shortage of PPE and Covid tests is almost equally as big an obstacle to getting a handle on this with no time to prepare.
I'm hopeful that with millions of doses chloroquine now being essentially immediately available, there's a chance for an unforeseen turnaround. But our national total lack of preparation means we still stand to get t-boned over the next 4-8 weeks regardless.
I think the linchpin will be early detection and treatment. The meds will almost assuredly be more effective at preventing/managing pneumonia if taken early as you mention, but that hinges on testing ---> so you just start giving out chloroquine for presumptive positives and tweener cases, which given the alternatives may be the best option under the circumstances.