1. I agree with Martin - this would be west of modern day Sudan and quite likely from the Tebu regions judging by blade decoration, blade style and the flattened pommel.
2. As Henk rightly points out these marks are usually talismanic - I am no expert on these particular marks but it is a common pattern on Tebu items.
3. Cleaning - light amounts of oil and steel wool - you don't sharpen it and you don't want to make it "shiny" all you want to do is remove any active rust and prevent it from rusting further.
4. Biggest mistakes you can make are over cleaning and sharpening - in general leave an antique much as it was when it came into your possession.
Its a nice piece overall.