1) showing abstract

Zotero is already showing the abstract for RSS feeds that are properly formatted.
You can give here some examples where you see problems, but they most likely come from the publishers.
Many publishers only throw roughly formatted text in their feeds, because they only want to make them "look ok" in regular RSS readers, without making the effort to format them properly. See here.

The best way to fix the problem (rather than customizing badly formatted feeds in Zotero) is that many people contact the publishers to ask them to fix their feeds. I have reported already to many publishers, but without much success so far.
Many publishers do their job properly, and their feeds look good in Zotero. But others do not care and do not react until they receive a massive amount of complaints.

[Graphical abstract would be nice also, as discussed in another thread.]

I have just reported on the ACS Publications Support: https://acs.service-now.com/acs
They have a chat option at the bottom right:
https://s3.amazonaws.com/zotero.org/images/forums/u265723/bdhp35jcn2xl59hfq41g.png

I have just prepared an example of a feed, told them that it was not properly formatted, and then simply gave them more details as they asked, including a screenshot in Zotero.
They nicely acknowledged the problems, and told me that they will send me an email when it is fixed. Having multiple people report the problem will probably increase the likelihood of seeing this fixed soon.

Another example sent to Elsevier from this page: https://service.elsevier.com/app/home/supporthub/sciencedirect/
"Your RSS Feeds are not properly formatted. So they do not appear in a well structured way as for other publishers. Can you fix this?
Bad example: JCP RSS Feed: http://rss.sciencedirect.com/publication/science/00219991
Good example: Journal of Fluid Mechanics RSS Feed: https://www.cambridge.org/core/rss/product/id/1F51BCFAA50101CAF5CB9A20F8DEA3E4
This is an old problem that Elsevier has failed to address for a very long time, as discussed in this blog post:
https://blogs.lse.ac.uk/impactofsocialsciences/2018/10/04/addressing-the-unharmonised-metadata-of-rss-feeds-would-support-research-discovery-and-speed-up-science/
Please make sure to follow the standards to properly format your feeds:
https://www.crossref.org/wp/labs/whitepapers/rss-best-practice/"

If they reply, I give more screenshots showing the problem in Feedly (if you mention Zotero to Elsevier, they will not look into the problem anymore...).

I don't know if there are better ways to report problems. I welcome any tips.

It is the same in my field: most journals have now adopted a graphical abstract that is available from the feed. So getting them displayed in Zotero (in the feeds and in My Library) would be really nice:
https://s3.amazonaws.com/zotero.org/images/forums/u265723/dxyf0ds366mitox4839p.png

It would be nice if rss feeds set up in the Mac desktop app would show up and sync in the iOS app. I use other feed readers and manage to get stuff over into Zotero, but it would be nice to just read and pickup items out of RSS and add them to my collections from the iOS app like can be done with Mac desktop app. What would be really handy in both apps would be if not only did you get an html “snapshot’ added to the parent record but also if a PDF was made to free the content and create something that could be annotated. Would really aid note-taking.