When you describe typing in the number requested, you don't mention the return key. It's not written in the main section, as maybe it should be: "type 598L2H then ENTER". But the return is required before pairing is complete.
I successfully paired several computers with the diNovo keyboard (the first generation version which was also not specifically "compatible" with OS X). Despite this official incompatibility, OS X's bluetooth software paired fine with the keyboard. But NOT through the diNovo bluetooth/mouse charger. That always failed for me. I had to use an internal bluetooth module or a third party dongle (success with Belkin and MS dongles). In this case, the special keys (aside from volume, mute and sleep) fail to work. No keyboard utility I've tried can enable the iTunes controller or other special keys. All normal keys have worked the entire time, with the caveat that you "swap" the start and alt keys through Apple's keyboard settings.
After two years however (about four months ago) this keyboard started losing it's connection mid-typing. I'm not sure what's at fault.