From your question you mentioned 2 or 3 competitors which means that you should still be able to achieve a first page position for the keywords you're targeting but perhaps not the top 3. In that case it comes down not only to optimization and link building; Is your site as useful as theirs?

A question I very rarely hear people asking in the SEO field is "I want to compete with someone for certain keywords, but is my business worth being ahead of the competition at this point?"

As well as content might be written, the moment you enter the e-commerce side of SEO the prices, delivery model/costs company reputation etc come into play a lot more than in the service industry. Especially if the product you're selling is the same one your competitor is selling. How many different ways can you describe a product?

My point here is the better the business model you are following the more likely people are to use your site than your competitors and in time you'll beat them in the SERPs. You should still put effort into generating content and building links but it will be easier if user experience on your site outclasses that of your competitors.

Hope this helped

Those services you mention which give out thousands of forum profile links are usually not worth your time or money, you see the same thing with generic directory listings, they are useless. Unless the forum topic is relevant to your website and they are do follow then don't waste your time.

I've found that signing up to 3 or 4 popular forums and being really active in them is a lot more beneficial in the long run.

You can easily build a website with wordpress and there's loads of themes you can choose from which you can then edit. Have a look at these an see if you like any. They're all free by the way - http://www.fabthemes.com/

Can you post a link to the page, I'll be happy to tell you how to do it.

Same here we've tested this out and it makes no difference at all. If it did in the past I wouldn't know but as of 2010 (which is when we tested this theory) the length of registration didn't make an impact on ranking.