Branded Content vs Content Brand
This is a loaded question, but I think the answer is inevitably "maybe". Being a "content brand" doesn't make sense for every brand out there, and I also caution against brands seeing content marketing as their only or best option by default. In this mad rush for every brand to become a content brand, customers are being forgotten, as are core competencies. Being a "content brand" won't make sense for everyone, and that's OK.
Your favourite content generation/marketing tools
I keep things pretty simple; almost comically so. I use Trello to keep organized and Word (gasp!) to write posts with, though I'm trying out Scrivener to see how I like it. For promo, I use Topsy, advanced Google searches, BuzzSumo (to see what others are doing) and basic, hands-on eavesdropping in public forums like Reddit, Quora, etc.
And then, good ol' fashioned email. It's not the tools - it's how you use them.
#1 Social media channel for content marketing
The problem with this question is that it assumes all audiences want, need or expect the same things. There is not and will never be a "#1" social platform for content marketing, because the content being marketed differs greatly, as do the people being marketed to. Snapchat, for example, is a brilliant platform for reaching young people and creating loyal audiences - but then again, Pinterest is a shoe-in for visual content targeted at audiences of women, and Instagram is a powerful community builder, too.
Instead of looking for magic bullets, marketers need to wake up to the fact that their audiences are human beings with habits and proclivities, and it's our job to reach them on whatever platforms they already use.
Long detailed vs short snackable content
Neither, because it's a false battle. Sometimes, long, detailed content is the best format for the audience. It seems to do well in search, and ebooks/whitepapers can work great as lead gen. But then, at another stage of the funnel, or with a different audience, short and snackable content is the best way to reach them because they are short on time/attention span in the context in which they consume that content.
Again, content creators and marketers need to eject themselves from this false dichotomy and stop looking for a universal truth in content. There is NO best content format, there is NO best content length. There is your audience and what they want - and your ability to give it to them. End of story.
The future of the Content-SEO pair
More collaboration, I'd suppose. We're already seeing SEO turn into less of a job unto itself and more of a consideration across multiple disciplines. I'd suspect that will continue. SEO is just one of a myriad of reasons to invest in content, and any time it becomes the ONLY reason or the sole focus, problems happen.