The only ones who get screwed over repeatedly are the good writers in terms of being paid slave labor rates.
Er, no. Copywriters have a skill. They write persuasive material. Content writers can also write persuasively, but the difference is basically that the content writer has more of an educational role. That's a gross simplification of the two, but it's a wee bit more elegant than saying copywriters "rape people's wallets."
If you are trying to get some work here on DP, it would be good to offer some free articles to established members (such as those who have an iTrader rating of 20 or more) in exchange for honest reviews. This would greatly help you to instantly build a reputation here. You could also give some discounts on your regular article rates to encourage clients to get your services. All of the elements that you have posted are important. However, you do not necessarily have to be a native English speaker to be able to write well. As long as you have had a good education (and you have excellent grammar) and if you naturally love writing, then you would surely be able to write well. Also, you could let your clients know about what your areas of expertise are or at least if you are willing to do plenty of research for topics that you are not too familiar with. For instance, you need not be a health expert to be able to write a good general article about heart disease. With a good amount of research added to a good writing style, you would be able to come up with a well-written and informative article. However, I would have to say that you would need to make sure that you have some knowledge about SEO writing, especially since many buyers today are looking for writers who have at least some basic SEO knowledge. I hope that this helps and good luck!