Looks cool. I think this is more suited to Instagram than Facebook. Even though Instagram is wildly popular, you still don't get to see as much third party tools like they have for twitter.
Also one question :
Would giving permission to post result in the app making postings without my knowledge?
My first business was a massively VC funded one and the second one is a completely bootstrapped one. There are advantages and disadvantages to both. But, I believe, a bootstrapped business allows - forces - you to think clearly, ask the right questions and build a "real" business.
Which brings us to your specific question - the answer based on my experience is to ruthlessly strip off things that are not needed at all like office space (work from home), legal (rely on templates but pay attention), recruiting ( do not recruit and/or outsource to freelancers), social media ( do it yourself or don't do it - I decided to NOT to do it and instead depend on SEO which scales better IMO), writing (write yourself - which will pay huge dividends for a long time).
Those are quick answers to your specific points BUT overall I'd suggest if you laser focus on "getting to revenue" and do only things that get you there and strip off things that won't get you closer to revenue or more revenue directly, then it helps you avoid tasks that are not critical. Keep in mind that some of the tasks you strip off right now may become important later - its important to identify what to delay and until when.
Its easier said than done, ofcourse, but much needed.