I am assuming the lengthier web page means lengthier relevant text and other content. This will make the ranking chances pretty higher.

Update the content on the page on the website and make that page or your website as a whole, engaging. This will reduce the bounce rate and the ranking will be restored.

didnt think so. thanks

There is no harm in using the same image. But the SEO benefit in the image search on the search engine will be lost.

No point because it's gated.

Off-page SEO of the site needs improvement. Currently, it is in poor state.

Get backlinks from your keywords to the specified page. By this, the specified will start appearing in the SERP.

There can be many reasons for it. Better, provide the URL to reach the exact problem and it's solution. Whatever the problem might be, it can be solved.

User specific run-time interactivity of a web page can be controlled using the Document Object Model. The DOM size should be in-check to keep the web vitals score green.

SEO, Google AdWords, and Facebook Ads will be helpful to fetch traffic on the blog.