Firstly, nice work in setting something like this up. Personally I'd edit your post and give the background information after you get into the nitty-gritty of what you want from your site - the reason being people don't have much time - so you may get more help that way. I'm disappearing in a moment so here are some thoughts that come immediately to mind:

Have you used the Google Keywords Adwords tool? You might find some of the terms you want to rank for don't get enough traffic to bother with. It will also give you suggestions for other potential keywords: https://adwords.google.co.uk/select/KeywordToolExternal

On your website I'm unsure what the various menu options mean. I wouldn't have known "Noah's Minute" was a set of videos for example, if I hadn't seen you mention it above. The 'Family' and 'Mom MD' options on the menu - I don't know what they are. I say this as usability is very important for SEO. If people don't find what they're looking for on your site they'll go elsewhere - and a high bounce rate can have a negative effect on your rankings. So keep adding the great content, but find a way to organise it in a more user-friendly way.

Maybe (if you haven't already) you could get other parents to write guest blogs on your site about their own experiences. If they or friends have websites/blogs of their own, ask if they'll link to their own posts. In today's celebrity obsessed world, it might be worth seeing if you could get one or two involved - by writing a blog, if they have experience with children with down syndrome. It would be a good way to raise awareness and get more attention (therefore links, therefore increased rankings).

It would be a massive effort, but a great thing to do would be to make the best page on the internet for down syndrome information. Make it factual, with sources. Making something better than Wikipedia and the BBC is usually a good start (http://en.wikipedia.org/wiki/Down_syndrome /  http://www.bbc.co.uk/health/physical_health/conditions/downssyndrome1.shtml). Perhaps it would be possible to do it in conjunction with a charity or organisation, who could verify what you've written (e,g, http://www.downs-syndrome.org.uk for here in the UK), or perhaps your personal experiences added to something like this would make it stand out over the more information-driven pieces. Maybe some down syndrome organisations could link to you anyway? See if they have links pages.

I hope that helps, sorry if I've been quick to the point on some things!

Wikipedia editors often delete pages about individuals or businesses if they deem that the individual or business isn't notable enough to have their own page. So in most cases probably not a good idea.

Are you sure the URLs are exactly the same? The following are all different URLs:

• examplesite.com
• www.examplesite.com
• www.examplesite.com/index.html
• www.examplesite.com/Index.html (note the capital 'I')

If they are different it's best to 301 redirect one to the other, or if that's not possible - add canonical tags to the two pages linking to your preferred version. Other than that, make sure you only use one unique URL throughout your site to link to one page.

I'd say it has a negative effect on SEO as SEO is also to do with user experience. moneysavingexpert.com used to have a pop-up that appeared just after the site loaded and blacked out the whole of the rest of the screen - I found it hugely annoying; just as I'd started to read the content it disappeared and I had to close something to continue reading. If I didn't already know the site was genuine I would have thought it was dodgy and pressed back or close straight away.

I'm not 100% sure but I think it was the owner of daniweb.com who said she introduced something similar to encourage people to sign up to her forum. Her bounce rate increased dramatically so she took it off as soon as she realised, and the bounce rate recovered. Bounce rate is something that can be measured by the search engines, along with other metrics related to user experience that will be taken into account when calculating the ranking of a page.

Alan's idea, to do something more subtle, is a good one. If it was unique and done really well, you might even get extra links because of it, rather than potentially less links as Matt Cutts suggested in the video Ryan linked to.

Make sure the language you use is natural. You might be able to rule out one or the other if it wouldn't be natural in your content.

Advice I've read in the past has recommended to optimise for both, though it depends on the term of course; some might be better as plural, some might not. Compare the search results for each and if one is more competitive than the other. Each might bring up completely different results, I think one example I read was that the singular showed e-commerce sites whereas the plural showed descriptive sites - I can't remember the example that was used.

Optimising for the plural is more likely to help with the singular than the other way around, but I think Google can usually tell they're related e.g. www.google.co.uk/search?q=red+bull+sticker - in more cases a longer tail keyphrase will probably show for both plural and singular, even if you just optimise for one of them.

What would be best for the user? I think it's about finding a balance between load speed and content without spreading the content too thinly across multiple pages, and being aware that constantly clicking to the next page can be time-consuming. Think about how the forum will be used - will people regularly come back to read one or two new posts? If so they won't want 40 posts loading on a page. Do users often make lengthy or short posts?

Things like signatures and images will slow the load speed down, so take that into account when you come to a decision. Perhaps make signatures visible to logged in users only, if applicable and possible? While 'content is king' faster speeds do have an SEO benefit too.

It's a balancing act, perhaps start with 15 and adjust that over time when you start to get a feel for the content that's posted.

It doesn't matter which you choose too much, as long as you're consistent across the website.

I'd go without a stroke; people are more likely to link to you without typing the stroke (as you say), so I think you'll retain slightly more link juice to the chosen URL if you don't include it (saving a 301 redirect from the '/' version). And personally I think a URL looks neater minus the '/'. The speeds "Optimize and Monetize" quotes are minuscule.

I agree that it's better to add it to your own site. What if people like your blog and link to it, but it's not on your site? You've lost some link juice there. You can submit it to blog directories too - more direct links to your site. For ecommerce sites there's a lot of content duplication with other sites when the same products are sold, so like you say in your last sentence, a blog adds regular unique content.

Perhaps a competitor or hacker are trying to displace them from the search results? One of the 'spam' results has "2,427 links to this URL from the past 32 days" according to Open Site Explorer - have you checked to see if any of that anchor text is the company name? I don't have full access to Moz at the moment so can't see.

http://www.opensiteexplorer.org/just-discovered?site=www.yolo2.cwsurf.de%2Findex.php%3Fpage%3DUser%26userID%3D4146%E2%80%8E

If you have nowhere more appropriate to redirect to I don't see a problem redirecting to the homepage.

I agree with EGOL.

Another problem with Wikipedia is that you don't have control over the content - anyone can edit a page.

Maybe one day your company will become well-known enough for someone to independently create a Wikipedia page about the company. At that point Wikipedia might be less likely to outrank your own site!