IIRC Markus isn't really maintaining this file these days so he might be willing to hand over the reigns if you approach him about it.

FWIW, ~ is just an operator (well, function), no? I don't think there are negative literals in the language (and ~x is valid for a variable x). Anyway, the wrong syntax being corrected there doesn't even highlight for me, since AFAICT the - isn't included in the match.

The additions for words look good.

No it is part of the literal. The grammar uses the same production for the exponent as well.

An integer constant (in decimal notation) is an optional negation symbol (~) followed by a non-empty sequence of decimal digits 0, . . , 9. An integer constant (in hexadecimal notation) is an optional negation symbol followed by 0x followed by a non-empty sequence of hexadecimal digits 0, . . , 9 and a, . . , f. (A, . . , F may be used as alternatives for a, . . , f.)

See https://smlfamily.github.io/sml97-defn.pdf