what to do with my wordpress, amazon, and pop singer domains

I have a fewdomains, that I don't know whether to keep them or just let them go. they are up for expiration and I'm trying to figure out if it is worth it to hold on to them.

The first domain has to do with wordpress training. I got it a couple of years ago on GD expired auction, when I was first learning about wordpress and getting into IM. The problem is that it has "wordpress" in the domain name, and since getting it I've come to understand that the Wordpress folk don't like that and will lean on you to give it up, since they don't want anyone to have the impression that the site has any official relationship to Wordpress the product. That's completely understandable, but in the meantime, is there anything (legitimate, long-term, scalable) that I can do with domain, other than to just let it expire?

The second domain, I got it one time when I was considering a WSO on setting up amazon affiliates sites that would be mobile friendly. the domain is about shopping, it is a .mobi, and the problem is (it didn't strike me at the time) was that it has "amazon" in the domain name. So, first, I wonder if that will get me into hot water simply because of using that name (in the context on shopping online), but also, isn't it the case that amazon would not allow an affiliate site to have that in the domain name? Same question, is there anything I can do with this domain, or would it just be easier to let it expire?

The third domain, it has the name of a popular singer in the domain it's a .info). I have a site (amazon affiliate site selling music) I started on it last year, but never really maintained it, and definitely not making any money, but it's got the potential for it if I turn my attention back to it. I got an email from someone claiming to represent this artist, demanding that I delete the domain right away. Do I have any options here, other than to simply comply? I've seen other (not at all official) sites with this singer in the domain, as well as sites that include names of brands, department stores, etc, and they seem to be chugging along fine.

Any advice from experience would be appreciated.