Yeah, the disassemblies are not perfect. Interrupt handling is especially fuzzy (though F4C30 _should_ be somehow covered).
Had hopes (in the past) that an Intel (or IDA) expert steps in and improves it.
With IDA 5 Freeware
you'd be able to improve the source AND follow the execution flow more easily (-> graph feature, jump back and forth etc.)
Unfortunately, i am away this week and can't provide the most up-to-date IDB file necessary.