Hi John, welcome aboard.
I agree with Rick that your keris appears to be made up of parts from different regions. Lovely ivory hilt. I have used small amounts of mineral oil on some of my ivory pieces. A soft Toothbrush works well as you have noted. But your ukiran does not look too dry in the pics.
I see the rust. on your blade. Can't tell for sure but it looks like it is a fairly surface problem. I bit of oil or WD-40 and a toothbrush might help alot. You shuld, of course, keep your keris oiled regularly. Many of us use a combination of sandalwood and mineral oil or singer oil and other scented oils.
If this doesn't help you may have no choice but to fully clean the blade, striping the stain. Depending on where you live there are people who can restain a keris for you. You are correct that it would be dangerous to leave any active rust on the blade.
There is a very good thread on how to clean a keris on the old forum here. A search of that forum should bring it up.
