Every time I see a compiler, the first thing a zero in on is the parser.

I don't mean this in a bad way, but that tokenizer looks a bit ... simple. ;-)

I say that because ~26 years ago I had a go at writing a C preprocessor with the goal of creating a ToC and Index for my C projects. I sat down with a BNF of C and lex/yacc and got ground up in the details, then found some software that did exactly what I wanted and moved on. I just remember a few parts of the C syntax that don't fit nicely into BNF and hadn't studied parsers enough to dig myself out of the hole.

Good luck doing it manually, that's gonna be tricky as heck.