Longer copy is acceptable. Including the full blog post text means a longer email, but there is a benefit to including the full blog text for your reader. You are offering them convenience by not making them click through to your site to read everything. You hold nothing back and give them everything for free, not even requiring a visit to your site. That can be seen as a form of goodwill, and readers often prefer the convenience of being able to read everything in their email client on their mobile device without having to open up a browser.
iii) List of questions in one email without the answers. Then, you can set up an Email Automation for those who click through your newsletter, to receive another email afterwards, with the answers to the challenges. (Because, on Moosend’s platform, email automation sequences only “cost” you one credit per subscriber, regardless of the emails in the sequence.)
In this context, I guess each post can’t be thought of in isolation, but in terms of a mini content ecosystem that comprises of a great blog post optimised for on-page SEO, an upgrade to that post tailored for that specific content, various on-page email conversion points including an exit pop-up or similar -and then you combine all this with your off page link building and outreach efforts. That could be over 5,000 words of content all in just that one package.