The correct way to handle this (and quite frankly, any javascript functionality) is to build it to work without javascript (keep the pagination), then have the javascript remove the pagination and implement infinite scrolling.  This ensures that visitors with JS disabled get the full experience of the site, search engines can easily crawl your full catalog, and users with JS enabled get the "enhanced" experience you desire from a UX standpoint.

It's not an "either or" scenario.  You can absolutely have an easily indexed site that extensively uses JS.

Yes, it's possible to outrank Wikipedia, .gov sites, and about.com -- the key is that you want to target terms where these sites have very few links pointing directly to the ranking page.  If they are ranking exclusively based upon their domain authority, but the pages themselves aren't inherently authoritative, they're much easier to surpass.

Even if those pages do get links pointed to them, it's not an impossible task -- you just have to create something really exceptional and pull in a lot of links.  Do a Google search for family history or genealogy and you'll see Wikipedia knocked down the SERPs by more commercial sites.

Also, as Alan noted if the term is one that will have a mix of informational and commercial searches, being below Wikipedia won't matter at all.  The key is to be the first site listed that's relevant to your target audience's search intent.

Good luck if you decide to pursue the terms!

There are plenty of sites ranking for competitive terms that use blog comment links as a huge component of their link profile, so yes, they still work.  They are effective for establishing link diversity (your approach) and also great for camouflaging a link profile (even nofollow links) -- making it harder for a competitor to sift through your link profile and spot the links that are really powerful and driving authority to your site.

Beyond those considerations, the real value I see in blog commenting is the potential to establish relationships.  If you comment thoughtfully and regularly on the blog of an influential player in your industry, you increase the likelihood of being able to acquire a legitimate link from them in the future, receive social mentions, or potentially create a partnership of some sort (sponsorship or affiliate arrangement).

If you do it right, there's some value there.  Just make sure you focus on your other (more effective) methods and use blog commenting judiciously.