As meta keywords - no. As part of your meta description - maybe. Like with your body text, it must flow naturally.

Your meta description should contain your main keyphrases, by which time you wont have much room left for anything else as Google only looks at the first 150 - 160 characters anyway. Anything beyond that a) will get truncated and b) looks like keyword stuffing.

In your case, I'd focus on sliding the LSI keywords in to your body content where natural and not worry about including them in your description.

p.s It should go without saying that 'meta keywords' holds pretty much zero value in SEO anymore. Even Yahoo doesnt care about them much these days.

Further reading: http://www.seomoz.org/learn-seo/meta-description

That depends on what percentage of your links are made up using those keywords. Negative SEO usually takes a LOT more effort than building a few crappy links to your website. The same has been done to some of my client sites in the past and it's not made any difference to their SERPs

Anyway, the simplest solution here is to login to Google Webmaster tools and use the Disavow Links tool so that at least they won't count towards your backlink profile.

http://support.google.com/webmasters/bin/answer.py?hl=en&answer=2648487

Hope this helps.

Google weights most of its SEO 'strength' to the actual domain name iteself - and even then, from left to right i.e the further right your main keyword is, the less juice it will get.

However, if you have relevant content on the page and name the page accordingly then you are making what is called an 'seo friendly' URL. Many people who use Wordpress for example, change their permalinks to change the url from something like mysite.com/p1 to mysite.com/keyword - which WILL make a difference, albeit not a huge one.
So if it's straightforward for you to do so, then by all means do it. Outside of SEO it will help your visitors better understand what the page is about, and will look a lot prettier in the SERPs too.

Also, rather than 301'ing each page, you may be able to change the structure of your permalinks within your .htaccess file so that it will happen automatically e.g by naming the file with the title of your page or postname.

Hope this helps...

Yup, these guys are excellent:

http://www.yourprivateproxy.com/

I've used them for search requests, map requests and even Scrapebox. Always available, low ping, not shared and reasonably priced for the 10 pack. Their user interface is simple and they get you up and running quick.

I'm starting to sound like an affiliate so I'll leave it at that.