It will direct the link juice from the redirected URL to your page, as long as you use a 301 (permanently moved) redirect. This will pass 90-99% of link juice from the linking URL.

To squeeze out everything you can get (pardon the pun) ideally you want a direct link, but a redirect will pass most of your juice along in the case you would have to get people to change hundreds / thousands of links.

If we look at a site like a human would, which is what search engines are evolving to do, then always matching exactly your Title and H1 tags is going to be pretty silly in my opinion.

Good practice is to use a few targeted keywords in the Title tag that describe your page well and the content within up to 70 characters. Of course not all pages will use the full 70 characters. That might cause stuffing penalties.

For H1 you might match some of what you list in the Title, but not exactly. You're going to have commas, pipe characters, other kinds of descriptions, brands, etc. Matching all of this would be crazy and would make a site appear very spammy.

Since the search engines are striving to be more and more human every day a good long term strategy is to build sites for humans first, and search engines a close second.

First - stay calm. Is your traffic noticeably dropping? Have you been penalized in any way in the SERPs? If not, you might just be experiencing regular fluctuations and have nothing to worry about. Look at that first.

Next, I'm assuming you have a Pro campaign set up.

The first course of action there would be to analyze your warnings, errors and notifications to minimize those. Fix the low-hanging fruit there and move on. Next, make sure you're following proper on-page SEO architecture throughout your site. Proper titles, H1s, interlinking, hierarchy, sitemapping, etc.

Now analyze your link profile. Do you have a lot of low quality links? If so, you may need to do some cleanup.

Additionally, you're in an e-commerce sector, so you may also want to check out the most recent Pro webinar - http://www.seomoz.org/webinars/ecommerce-seo-fix-and-avoid-common-issues

There are a number of things that can contribute to this. Without more information, all I can tell you is to start with the basics and move up. Have you made any significant changes lately?