I am not familiar with the specifics of the 99 front sight, but it sounds like you are on the right track the blade is dovetailed into the sight base I don't know if that is the correct direction or if it can slide out from either side.

I have a Williams front sight pusher tool for adjusting and removing Williams front sight blades. Do a search for it on MidwayUSA's site. I don't know if it would work on the 99, but if you think it might help, PM me.

Also, make sure you support the opposite side of the barrel and sight base with something (you could easily fabricate something out of wood) as you bang on it.