You'd probably get better answers to your Masm questions on a Masm forum. If you wanna "translate" it to Nasm syntax, maybe we can help (PITA - looks like it uses a lot of "Masmisms")
Lines 101 and 118 wouldn't assemble with Nasm (without modification), but they look okay to me for Masm - maybe a different version(?). There's some kind of command line switch or directive to make newer versions behave like older versions, I think. If you can find that, it might help.
Line 239 may be because Masm differentiates between labels and variable names - try it without the "offset".
The reference to "coff" is a sign of trouble. You don't want this assembled to coff format! Find out what switch you need for OMF output. One advantage of translating the whole mess to Nasm is that we could spit out a .com file directly, without messing with a linker and "exe2bin"...
Best,
Frank