I'm not sure there are any font creation packages for OS X. If you have a dual-boot Mac and can boot into OS 9, you can try Macromedia Fontographer (if that's even on sale these days!). Fontographer can create PostScript® Type 1 fonts and TrueType fonts for both Mac and PC.
It is, of course, illegal to adapt an existing copyrighted font, but that's not a problem as you will be creating your own from scratch I hope!
Illustrator cannot create fonts. Depending on the amount of text you need, you could conceivably convert the roman version of a font to paths and slant it in Illustrator *but that would be oblique, not cursive. You can create the basic letter shapes in Illustrator, save them out as EPS files and then import them into Fontographer to create a font, but Illustrator itself canot handle the technologies required to make a Type 1 or TrueType font.