So again, I don’t have access to your GSC and I haven’t analyzed your indexing, but from what I can see you do not have any pagination issues.
Webflow is doing what it’s supposed to, and so is Google. You just have poor pagerank, so you’re not seeing the SERP results you want, because Google has very little to work with in terms of ranking info.
Focus on that, as I suggested.
No you cannot add a second canonical safely, you’d just send conflicting signals to Google, and it will most likely choose the first one ( Webflow’s ) anyway.
Most of the things you’re trying to do don’t actually solve any problems, and just make the SEOability of your site worse by confusing your signals to Google.
Keep it clean, focus on content and backlinks.
In rare cases I do modify client sites specially for SEO purposes, e.g. to create semantic paths from CMS content like /france/paris/cafes, or to change the information in the sitemap.xml. But this requires a reverse proxy and adds a lot of infrastructure on top of the site. For 99% of sites I wouldn’t even consider this- Webflow’s SEO approach is solid.