Apologies. Didn't see this thread until today and didn't see the date, either.
Anyhow: I know of two articles published about 9 years ago that address these topics pretty well. Send me a PM with your e-mail and I can provide PDFs of these articles if you're interested.
Assuming you're after fairly rough-and-ready engineering values, I'll try offering some comments:
1. The enthalpy of fusion is a rather weak function of temperature. For most engineering purposes, assuming it's temperature independent is not a bad approximation.
For the rest of the...