The images on your page should be relevant to your pages content, so describe them with an alt tag naturally will add relevance. The length is not important, but I would not stuff they will a long list of keywords.

Links don't have to be relevant, its not to say that non-relevant links don't carry any link juice at all, but it is better to have relevant ones.

But I doubt that this guys links have any benefit at all. And if he is using some black hat schema to get these links, then one day that link network maybe or already discovered and you may get a penalty.
This happened in the past where a large number of link networks that sold links were put out of business overnight.

Get him to remove all the links and get rid of him.

sometimes it is better to get a new domain and start again. And do not 301 old domain to your new one.
There are things to consider before doing so, but it sounds like to me your links are crappy,, and who knows what else they have done.

Take a copy of the htaccess file, if something goes wrong, then you can always go back

No,
it is because you are pointing sales to a different sever, it seems to me that you don't have your dns set up correctly. you don't want sales pointing to your main website.

The logic I used is like this.

rather than have a rules like
If wearing jeans, you must wear the school uniform
If wearing hoodie, you must wear the school uniform
If wearing a thong, you must wear the school uniform
If naked, you must wear the school uniform

you only need one rule
If not wearing school uniform, you must wear the school uniform

in htaccess "!" means not so try this

RewriteCond %{HTTP_HOST} !^www.domain.com$
RewriteRule (.*) http://www.domain.com/$1 [R=301,L]

also when using regex special chars like "." should be escaped with "" see above www.domain.com

Ok, I think I understand a bit better, you don't have a blog?
Then I would remove the dns record for blog, if you cant do that then yes you could 301 redirect

You can do this in one redirect following the logic
if not www.domain.com then redirect to www.domain.com

Sorry missed the bit about blog.
obviously blog.domain.com should not 301 to www
it should point to the correct site, then all reports and google will sort themselves out.

so add one more step, test that blog does in fact resolve to the correct site

You need to point your cname to the ip of the server that hosts your sales.domain.com

don't

sales.domain.com > domain.com

Do

sales.domain.com > 123.123.123.123

where 123.123.123.123 is the ip of the hosting webserver.

Test that non-www 301's to www
Make sure that all your internal links point to www, you don't want links that you control going thought a redirect.

If those 2 are ok, then forget the report it will sort itself out over time.