What bottom bracket removal tool do I need? I haven't been able to find a bottom bracket tool for this specific spline count/pattern. It looks like it might fit a standard 20-spline one, but I'm not sure since there are actually only 16, but with larger gaps in between groups of 4:
It's just the regular old 20-spline cartridge type tool, i.e. Park BBT-22. I have seen a few like this, although I don't really know what the deal is with them.
While there are now an enormous number of outboard type BB tool spline patterns, internal cartridge BBs pretty much exclusively use either the Shimano-originated 20-spline tools or the smaller Campy spline pattern.