1: 36.7 to 38 is nothing. It's shit when you account for the ever-increasing ticket prices and incessant inflation. You're also getting a huge boost from Asia, which adds a lot to the global revenue numbers but not much to Hollywood's pockets.
You need to look at ticket sales, which peaked in 2002 and have been in steady decline ever since. This is despite a massive increase in production budgets and advertising, and an 11.5% increase in US population, US ticket sales in 2015 were 16.3% lower than in 2002.
2: 2015 included 2 major outliers. Jurassic World and Star Wars Episode VII:The Force Awakens.
3: Yeah, China (and the rest of Asia) are huge. The problem is distribution costs and channels in Asia, local pricing, and all the other shit involved with international releases means that the people making movies in the US see pennies on the dollar from Asia's revenue. This is before Hollywood accounting - this is real.
This isn't new or surprising. The result is the same thing we've seen for the past few decades. Big studios become increasingly reliant on blockbusters. In the 80s and 90s, if a movie didn't turn a profit after 6 weeks in the US they relied on rental and home release revenues to put them in the black. This lifeline became stronger when DVDs reached critical mass, but shortly after streaming started eating into that.
Many studios had signed streaming contracts that ended up screwing them over because they accepted a low bid as free money - icing on top of the DVD sales. This is what ultimately caused a big kerfuffle that continues to this day with Netflix and other providers being unable to secure the rights to to a library worth writing home about. Studios saw DVD sales evaporate and saw Netflix and competitors becoming behemoths, just like iTunes did with music. They jacked up the costs, took the ball and went home to make their own streaming / digital download services, sign exclusivity deals for more cash from a specific service, etc.
While this was going on, studios started to rely more on the international revenue because it was a generally untapped market. Stars in big films now spend as much or more time on press junkets abroad in countries that can't understand a word they say. International revenues supplanted the rental / home sale revenues after BluRay failed to take the world by storm and served as a stop gap during the streaming depression when studios were locked into cheap agreements.
However, even with the growing Asian market, and new contracts for streaming that generate big cash for studios, the rising production and advertising costs and tumbling ticket sales in the US have studios terrified. The effect this continues to have on films is obvious. It's been a trend since the 80s and 90s. Studios rely more and more on focus-tested, formulaic drivel, mega blockbusters, and keep jacking up ticket prices as much as the market will bear. (Remember the 3D tax?) Additionally, if a movie isn't a hit it'll be pulled from rotation in 2 or 3 weeks instead of the 6-8 or more, and there are fewer and fewer cheapo theaters that run movies a month or two after initial release. (A few decades ago they were called "dollar theaters", several years ago they were barely any cheaper than the megaplexes.)
And what do you do when you pull a movie because it bombed? You slot another in its place. ASAP. You bolster your lineup with guaranteed hits. (Disney will churn out new Star Wars films rapidly from now until they stop making money.) You space out your titles not just against competitive releases, but against your quarterly reports. You don't let a director do a pet project unless they also sign on to put their name on some by-the-numbers blockbuster piece of shit. You do more and bigger media buys. You hire a PR team to run Twitter accounts for the stars in the run up to release. You have a huge event at the San Diego ComicCon despite your movie having nothing to do with comics. You fly people across the globe on a non-stop press junket orgy.
None of this is sustainable long term and the studios know it. That's precisely why they've tried gimmicks recently like buying an unlimited yearly movie pass for the price of 8 movie tickets (and hoping people only go 6 times), IMAX releases for films that have about 40 seconds shot on IMAX film or a resolution that would benefit from it, 3D for the third time. They need to sell more tickets at higher prices above all else.
And that's also the reason they're looking at same-day / soon after digital releases. Movie theaters are dying. Partly because costs are going up, partly because the experience is awful, and partly because streaming/bluray is more convenient. But a major component is that the streaming services (even including free shit like YouTube) and even cable offer new content that people are spending their time on. From Breaking Bad to Game of Thrones, cable productions have had a renaissance in recent years, further deteriorating box office sales, and streaming services like Netflix and Amazon are producing their own content, without the cruft of the old guard.