Advise on Social media / blog order / flow

Hi all,

So I'm looking at starting up a brand new blog to build a blog / email opt in list (want to go that route to protect myself from loosing social media lists in future) and i'm also planning to use these social media streams to help spread the Blog and build the email list....

Facebook page
Twitter
pintrest
and possibly Instagram

i'm eventually looking at driving all of this traffic back towards my blog and an email opt in, plus my ecommerce site and amazon to sell my product (which is my main eventual goal)

I'm just a bit lost which way to stream the social media and wondered if anyone out there runs a similar bunch of outlets and could help with any advise / tips.

my thinking was to go this route...

1. write the blog on wordpress (schedule them using a wordpress plugin)

2. then use a second wordpress plugin to instantly copy this blog post to all of my social media streams

but then i started to think that the format of the blog (esp if its a fairly long blog post) will not work with Twitter and instagrams formats with hashtags etc.

so is there a good way to help automate and format or do i literally have to manually reformat for each social media stream to suit its format?

plus for Facebook, should i just have the first paragraph and a picture from the blog and then a link to READ MORE to drive traffic back to the blog and the therefore the email opt in?

and would for instance Twitter and instagram work as one version being a similar format and then the blog and Facebook work together and then i'll just have to reformat for pintrest?

or am i getting a bit confused and over thinking it!! haha

also any advise on the best way to funnel all of this to get as many email opt ins as possible would be great. For eg should i do a Read More link on all posts for all social media or is that overkill?

any advise great received please!
Thanks