Cost of furniture in Abidjan
If you're shipping from Europe/Can/USA, go to Ikea and buy everything in sight. Chances are, you'll be able to use it in your new place, or sell it for a profit. Everything is expensive, including tupperwares....
If you are willing to buy local, you may end up with nice, relatively inexpensive furniture. But you are going to have to go to a carpenter and have it made. It'll be even cheaper if you supply the raw materials, since he won't be marking up the price of the wood. I haven't had to buy furniture and don't think I will (my room mate's company has graciously agreed to furnish for us), but I will ask around...
Another good source is AfrikAnnonce and Internations. Abidjan is a place where tons of people are constantly coming and going. People leave and need to sell their stuff, often at firesale prices. Get in while you can, and bid low -- you might just get lucky.
Security/moving around the country:
I find this to be really overblown. Every major organization/ company has liability issues, so they would rather you stay out of harm's way. That said, Ivory Coast is a safe country. It may not be forever, but it is safe right now. I have heard of the "coupeurs de route" but have yet to have met anyone who has been affected by it. In my short time here, I have met a couple of young French engineers who work on the Liberian border, and they seem to be doing just fine. I also met a young guy working for an animal feed company and he is all over the rural areas of Ivory Coast. he sticks out like a sore thumb but seems to be having an incredible time. I'll post about more weekend destinations in my upcoming travel post.
Your questions are kind of what makes doing this worthwhile! Don't hesitate to tell me what you'd like to see more of!