I, for a long time, have felt domain age seems very important when ranking a site. I have seen sites which I just couldn't figure out did well apart from that aspect. They had very little content, broken pages, not a huge amount of backlinks, so what else could it be.
This was the day, not so long ago, when you could use yahoo explorer. Since a few Google updates, some of these sites have deservingly dropped IMO.
Your site is young, but you should be ranking for keywords that aren't that competitive. Use Adwords to check the competitiveness of the keyword. I ranked quite high quite soon for these type of keywords.
Everything has changed now and I think a lot of people are scared to build links since Penguin, but building links is still a key part of SEO. Build them in the right places and slowly. If you can, create regular content to the site, and have your keywords spread across these pages in a sensible fashion.
It is very frustrating and I replied to your post as I was obsessive about all this in the early days too. Look at it as a long game (hopefully) keep doing what your doing, invest time in the right areas and do the right thing and hopefully you will see you site start to rank. I've gone from PR0 to PR 4 in about a year, but it's been a lot of hard work. PR before someone jumps all over this is just one factor, but it's a good indicator of how your site is doing, which can go up or down.
Content/Links/Structure are the things you should be concentrating on. 3 months is very early days unfortunately. Create sitemaps, submit every new page to google/bing e.t.c and get some deep linking to other pages. Try to get people to naturally link too which I understand might be hard in your niche.
Things change all the time, site go up, go down disappear. I personally think that GOOGLE still don't know what they are doing are always changing thing because they are always getting gamed. I'd hate to have their job. To this day I still see useless results returned.