While I agree with what Nicholas said, I've seen more and more instances of "near me" in titles when I search for something near me.
Check out the SERP for your queries in your area and see if others use it.

If you mean themes, then I would say yes.

I changed a theme on my blog recently and it resulted in major organic impressions growth. I'm pretty sure it's the theme because I didn't change anything else.

http://isearchfrom.com/ 

With I Search From you can simulate using Google Search from a different location or device, or perform a search with custom search settings. It's useful for searching Google as if you were somewhere else, as well as for SEO & SEA testing.

If you don't want to remove these from index and want them to provide more value try adding more fields and up the requirements for the minimum amount of text in the description.

Moz's user profile page is a good example https://i.imgur.com/C4YR7AE.png
There's not exactly a lot of content, but every field is unique for every user

I would leave it.
If there is a link to the old page somewhere, you'll get a 404 instead of 301 if you trash it. I'm talking about external links, I guess you've taken care of the internal ones.

If you delete the page any direct or referral traffic to that page will result in 404 instead of 301.

Definitely depends on the topic/audience, like you said. It never hurts to run some tests, and don't take anyone's personal opinion on it. I would say that black check marks are better, but I may be 100% wrong in your case.
Lime green frames improve CTR in some banner ads, despite looking hideous and spammy, same for red/yellow text/background combinations and other questionable things.

Even if flow metrics on those links are good, the sudden spike is already a red flag for search engines.
If those links aren't organic get rid of them.
I'd get a list of referring domains and bulk check the domain metrics (age, pr, trust flow and etc) and if there's nothing good - get rid of them.

There are alternatives like Serpstat's "related keywords" and Ahrefs' "also rank for". they determine "LSI" keywords by finding connections in SERPs.
Take top 10 for keyword A and compare it to top 10 for keyword B, if 5 pages from SERP A were found at SERP B it's safe to assume that keywords A and B are related.

You can find some cool keywords with these tools
Example: https://i.imgur.com/wO62vII.png and more https://i.imgur.com/HWiBchu.png

Here's what fitment is for those unfamiliar: https://i.imgur.com/RptDZ1e.png

No, it's not in thousands, if you see 11 – 50 it means that there were less than 50 searches with this keywords last month in your chosen region.