1) Yes, but that doesn't mean it will keep clients happy. If you're going to quote by the job that is how you need to do it.

2) Go for it, you should be able to attach it to a post. There arent any professional lawyers but a number of people here (myself included) know our way around and could provide informal feedback.

3) It all depends on the quality of the work. $50/hr may be a little steep for online work but for face to face work that should be fine. Don't advertise that though since you quote.

4) Go for it, it wont be moderated unless you are blatantly advertising.

5) This forum is a good place, you just have to wait a few days. I get most of my general PHP leads from ads I post on this forum, I also have a niche market I get from webhostingtalk. Overall the online market is crap, get used to losing clients who think some Indian outsourcer can do as good work for 1/10 of your price. Don't waste your time with elance (or any other bidding site), digitalpoint or sitepoint, good work stopped going though them years ago.

Also make a distinction between designing and coding. It is impossible to design in PHP and it makes your statement that you design in Wordpress ambiguous.