I have a MacBook 15" Pro, with BootCamp. SH3 runs fantastic with all kind of supermods.
I don't use the + and - for TC, just click with my mouse and normally I don't go higher than 128 TC.
You can use an external USB keypad if you want.
Find help at BootCamp (the square grey box at the bottom right Windows XP), right click on Boot Camp and choose Boot Camp help.
Type in for example: "keyboard", you will see all sort of commands.
Print Screen = Fn+Shift+F11
Print Screen during game = Fn+Ctrl+Alt+F11