Q1 is almost impossible to anwser. But just so you know, I'll write you 1000 articles for just 45K!
I would suggest a completely different approach, but that's just me. Suppose you have 1000 articles right now. I honestly think it would be a mistake to put them all on one site. I would take 200 articles and put them on my main site, and I would phase out the release. I wouldn't just dump 200 articles at once.
With the remaining 800, I would simply give them away to all sorts of other websites with each including a couple of backlins to my main site.
What this does is it allows you to have a comprehensive main site where you can SEO the hell out of each page, then by giving away the rest, you actually setup back links to target yoru specific keywords on your various pages you want to promote. I'd have about 1/3 of the 800 articles giving backlinks to my front page, and 2/3 linking to various internal pages.
This is what will generate your search engine traffic. The article itself isn't really driving the traffic. Oh sure, someone could stumble uppon an artile, find it interesting and click the links to end up on your site. But don't put all your eggs on that basket. You want to move up the SERPs with the keywords you target. This will do it for you.
Back to Q1, one reason why it is so dificult to predict the traffic you can expect has to do with your keyword selection. This is truely the most important factor in this entire plan, and if you manage to screw that up by either selecting keywords from a market that has too much competition that you can't beat, or ismply target keywords that nobody searches for, this greatly affects the overall results. You can have a billion articles, if they don't target the right keywords, you've wasted them.
Q2 - If you did what I proposed above, then the 800 articles out there that are linking back to you permanently help you maintain your SERP. But you can never just walk away. Your keywords are your bread and butter and eventually, you'll need to remarket them to ensure you don't start droping rank in the search results. Competitors will eventually figure out your strategy, mimic it, and beat you at it if you just walk away. It's a constant battle.
Those are my own thoughts on the whole thing.